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PubMedDate not supplied

CRT diagnosis of pulmonary disease: influence of monitor brightness and room illuminance on observer performance.

Using a 21-in. cathode ray tube (CRT) monitor (2048 x 2560 x 8bits), six radiologists interpreted 12 images with interstitial lung disease under six conditions of CRT luminance (50 and 400 cd/m(2)) and room illuminance (20, 120 and 480lx), and 10 radiologists interpreted 25 images with pulmonary nodules under nine conditions of CRT luminance (50, 200 and 500 cd/m(2)) and room illuminance (20, 120 and 480lx). Observer's performance for interstitial disease was relatively better at 120lx. Four hundred and eighty lux illuminance with 50 cd/m(2) CRT luminance, which degraded the detectability of pulmonary nodule significantly (p<0.05), should be avoided for clinical use.

Data Display↗
PubMed2000

The influence of a perceptually linearized display on observer performance and visual search.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether perceptual linearization of the tone scale affects the detection and visual search behaviors of radiologists searching mammograms for masses and microcalcifications. A perceptually linearized display is designed to match the capabilities of the human visual system more closely than a nonlinearized display. MATERIALS AND METHODS: Six radiologists viewed 50 pairs of mammograms, once on a perceptually linearized cathode-ray tube (CRT) monitor and once on a non-linearized CRT monitor. Eye position also was recorded as the observers searched the images for masses and microcalcifications. RESULTS: Observer performance was significantly (P = .003) better with the perceptually linearized display. Dwell times associated with true-negative decisions were significantly longer with use of the nonlinearized display. The number of fixation clusters generated during search was also greater with use of the nonlinearized display for the lesion-free images. CONCLUSION: A perceptually linearized display yields better detection performance and a more efficient visual search. Perceptually linearized displays should be used for reading radiographs displayed on CRT monitors.

Breast Neoplasms↗
PubMed2000

Binocular three-dimensional perception through stereoscopic generation from rotating images.

RATIONALE AND OBJECTIVES: The authors evaluated the clinical utility and potential applications of a binocular three-dimensional (3D) image display in diagnostic radiology. MATERIALS AND METHODS: Rotating video displays of computed tomographic (CT), magnetic resonance (MR) angiographic, and digital subtraction angiographic (DSA) image data were used to generate stereoscopic image displays with a 3D appearance. Eight physicians viewed and scored eight skeletal and eight vascular-interventional studies with a planar display mode and a cathode ray tube. Each physician then viewed the 3D display of the same data and assessed the change in image findings, as well as any corresponding changes in level of diagnostic confidence. RESULTS: Image findings changed in 78 (61%) of the 128 studies after viewing the 3D displays. In 94 (73%) of all 128 studies, the interpreters reported increased confidence in their perception of the findings. Results for the vascular-interventional and skeletal cases were generally very similar. CONCLUSION: Binocular 3D stereoscopic displays from rotating images were reported to provide better image conceptualization and a higher degree of confidence in the findings on the images.

Angiography, Digital Subtraction↗
PubMed2003

Using a human visual system model to optimize soft-copy mammography display: influence of MTF compensation.

RATIONALE AND OBJECTIVES: The investigators developed an efficient method for optimizing cathode ray tube (CRT) monitor performance for digital mammography, based on the correlation between the performance of human observers and the performance of a mathematical computer model of the human visual system. The investigators examined observer performance on soft-copy display of mammographic images that were either unprocessed or processed to compensate for modulation transfer function (MTF) deficiencies in the CRT display. The results were used to validate the human visual system model. MATERIALS AND METHODS: Six radiologists viewed a series of 250 mammographic images with microcalcification clusters with different contrast levels on a CRT monitor. The images were viewed twice: once without image processing and once with processing designed to compensate for MTF deficiencies in the CRT monitor. The images were analyzed with the JNDmetrix Visual Discrimination Model, which is based on the principles of just-noticeable difference measurement and frequency-channel vision modeling. Receiver operating characteristic (ROC) curves were generated for the human observers and compared statistically with the model observers' performance. RESULTS: Both human and model performance was better overall with the MTF-compensated images, especially for microcalcifications in the midlevel contrast range. There was a very high correlation between human and model observers. CONCLUSION: The use of image-processing methods to compensate for limitations in the MTF of CRT monitors can improve the detection performance of radiologists searching for microcalcifications in mammographic images, and a model based on characteristics of the human visual system can be used to predict human observer results accurately.

Computer Simulation↗
PubMed2003

Using a human visual system model to optimize soft-copy mammography display: influence of display phosphor.

RATIONALE AND OBJECTIVES: The authors developed an efficient method for optimizing cathode ray tube performance for soft-copy digital mammography displays, based on correlation between the performance of human observers and the performance of a mathematical computer model of the human visual system. The authors measured radiologist performance on soft-copy display monitors with different phosphors and used these results to validate the human visual performance model. MATERIALS AND METHODS: Six radiologists viewed a series of 250 mammographic images with microcalcifications of different contrast levels. They viewed images on two soft-copy display monitors with phosphor luminescence-one with P45 and the other with P104. The same images were analyzed with the JNDmetrix Visual Discrimination Model, which is based on psychophysical just-noticeable difference measurement principles and on frequency-channel vision-modeling principles. Receiver operating characteristic curves were generated for the human and model observers' performances, and results were compared statistically. RESULTS: Both human and model performance (area under the receiver operating characteristic curve) was better overall with the P45 than with the P104 monitor, especially for microcalcifications in the midlevel contrast range. There was high correlation between the human and model observers. CONCLUSION: The results indicate that the type of phosphor in a display monitor can influence observer performance significantly and that a model based on characteristics of the human visual system can be used to predict human observer performance accurately.

Breast Neoplasms↗
PubMed2002

Pulmonary nodule detection and visual search: P45 and P104 monochrome versus color monitor displays.

RATIONALE AND OBJECTIVES: The faceplate of a cathode-ray tube (CRT) display monitor is covered on the vacuum side with a phosphor screen. The different phosphors that can be used for this screen have distinctly different physical properties that can affect the noise properties of the display. Differences in noise affect the signal-to-noise ratio and, hence, may affect diagnostic performance. This study evaluated observer performance and visual search parameters in the detection of pulmonary nodules, comparing two monochrome CRT monitors with different phosphors (P45 and P104) and a color CRT monitor. MATERIALS AND METHODS: The receiver operating characteristic paradigm was used to evaluate observer performance with a series of radiographic chest images containing solitary pulmonary nodules. Eye position was recorded as the observers searched the images on each type of monitor. RESULTS: Observer performance, as indicated by the area under the receiver operating characteristic curve and compared by means of an analysis of variance test, was best for the P45 monitor, next best for the P104 monitor, and worst for the color monitor. All differences were statistically significant. Eye-position parameters were also affected by monitor type. The time required to fixate the lesion and overall search times were longest with the color monitor. CONCLUSION: The type of phosphor used in the CRT monitor faceplate can affect diagnostic performance and visual search parameters. Care should be taken in the selection of monitors for use in clinical radiology.

Analysis of Variance↗
PubMed1994

Improved visualization of stimulated nodules by adaptive enhancement of digital chest radiography.

RATIONALE AND OBJECTIVES: Although digital radiography of the chest has a wide dynamic range, difficulties still remain in visualizing the acquired images faithfully on gray-scale displays (cathode-ray tube [CRT] displays), which have a much lower level of luminance than film view boxes. We propose an adaptive-enhancement algorithm for digital chest radiography that provides faithful visualization of the chest on the CRT. METHODS: We investigated the contrast sensitivity of a CRT monitor and developed an image processing algorithm that compresses the dynamic range and enhances image contrast selectively in the mediastinal area and that transforms the gray scale to visualize the image by use of the full effective dynamic range of the CRT. We performed a receiver-operating characteristic (ROC) study by using simulated nodules to evaluate the clinical value of the proposed algorithm. RESULTS: The processed images provided improved visualization of both mediastinal and lung regions. The area under the ROC curve for retrocardiac or subdiaphragmatic nodule detection increased significantly (from 0.69 to 0.79; P < 0.05). The area under the ROC curve for lung nodule detection also increased (from 0.64 to 0.75; P < 0.1), although not to the level of statistical significance. CONCLUSION: The proposed algorithm allows improved visualization of nodules on digital chest radiographs with the CRT display.

Algorithms↗
PubMed1999

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

RATIONALE AND OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Contrast Sensitivity↗
PubMed2000

Suitability of the general-purpose graphic printer as an image output device for digital dental x-ray images.

OBJECTIVES: The purpose of this study was to evaluate the suitability of the general-purpose graphic printer as an image output device for digital dental x-ray images. METHODS: The image quality as obtained by a thermal printer and by a dye sublimation printer was investigated. A grid pattern image was used to check parallelism and verticality of lines in each hard copy. A step-wedge image was printed with each printer, and the optical density, gradient, and root mean square granularity were compared. Depiction ability was also compared by using test images, including small signals. RESULTS: All of the lines were parallel and vertical on hard copies of both printers. The dye sublimation printer showed better results on optical density, gradient, root mean square granularity, and depiction ability. CONCLUSION: The dye sublimation printer produces images of the depiction ability comparable to the cathode ray tube display and seems suitable as an image output device for digital dental x-ray images.

Coloring Agents↗
PubMedDate not supplied

Video-rate and continuous visual stimuli do not produce equivalent response timings in visual cortical neurons.

Video cathode ray tube (CRT) technology has proven to be extremely valuable for performing research in the visual system. However, the image on a CRT monitor is not constant, but consists of a series of brief pulses. This has implications for any study that explores the responses of neurons in the visual system on short time scales. In particular, there is no unambiguous time point at which a visual stimulus presented via CRT may be said to have ended. Recordings from single units in visual cortical area V1 of an awake primate demonstrate that, when studying changes in response timing on the order of 10 ms or less, stimuli delivered at video frame rates do not duplicate the effects seen with stimuli that have continuous functions of luminance versus time. Additionally, there does not seem to be any clear method of comparing the results obtained with video-rate stimuli with results obtained with continuous-time stimuli that holds for all conditions. These effects are especially critical when exploring the time course of the neuronal responses to the ending of a visual stimulus (off-response). Our findings cast doubt upon the recently reported result that off-responses have consistently shorter latencies than on-responses.

Animals↗
PubMedDate not supplied

Psychophysical estimation of the best illumination for appreciation of Renaissance paintings.

A variety of light sources are used in museum environments where the main concern is to prevent damaging effects of the light on paintings. Yet, the visual impression of an artistic painting is strongly influenced by the intensity and spectral profile of the illumination. The aim of this work was to determine psychophysically the spectral profile of the illumination preferred by observers when seeing paintings dated from the Renaissance époque and to investigate how their preferences correlate with the color temperature of the illumination and with the chromatic diversity of the paintings. Hyperspectral images of five oil paintings on wood were collected at the museum and the appearance of the paintings under five representative illuminants computed. Chromatic diversity was estimated by computing the representation of the paintings in the CIELAB color space and by counting the number of nonempty unit cubes occupied by the corresponding color volume. A paired-comparison experiment using precise cathode ray tube (CRT) reproductions of the paintings rendered with several illuminant pairs with different color temperatures was carried out to determine observers' preference. The illuminant with higher color temperature was always preferred except for one pair where no clear preference was expressed. The preferred illuminant produced the larger chromatic diversity, and for the condition where no specific illuminant was preferred the number of colors produced by the illuminant pair was very similar, a result suggesting that preference could have been influenced by chromatic diversity.

Affect↗
PubMed2000

Technical aspects of multifocal ERG recording.

There are a wide range of variables which can influence the quality of the multifocal response. It is possible to place these variables into one of four categories. First, the method of stimulus delivery will determine the field of view, interference levels and the duration of on-state stimulation. Second, data acquisition variables such as electrode type and placement, amplifier specifications and filter bandwidth settings will have a direct impact on waveform shape and on the topographic distribution of signal amplitudes. Third, patient variables such as fixation, pupil dilation and refractive error will also contribute to the multifocal response. Fourth, there are many measurements that can be taken from multifocal recordings. In addition to standard amplitude and implicit time measures (the implicit time measure in the multifocal response is becoming increasingly important particularly in early stages of disease processes), the scalar product measure provides information on waveform shape. The conventional impulse and higher order responses will be different for different modes of stimulation such as Cathode Ray Tube (CRT) and Liquid Crystal Display (LCD) systems and latency shifts will be introduced if not corrected in software. Procedures which could lead to misleading interpretation include artefact rejection, averaging with neighbours and summing of responses. These procedures should be handled with caution.

Electroretinography↗
PubMed2001

Long-wavelength red light emission from TV and photosensitive siezures.

PURPOSE: We investigated a role of long-wavelength red light emission from TV in the induction of photosensitive seizures by an animated TV program called "Pocket Monsters". METHODS: The luminance energy of recorded color bar was measured by a spectroradiometer in cathode-ray tubes (CRTs) of photosensitive patients with and without seizures on the program (induced patients and photosensitive controls). RESULTS: The mean ratio of long-wavelength red light to total visible range was significantly higher in the CRTs of induced patients than in the CRTs of photosensitive controls. The ratio of luminance energy between at turn-on and at 60 min after turn-on of the CRTs indicated that luminance energy in long-wavelength red range from the CRTs of induced patients increased significantly after turn-on of CRTs. CONCLUSIONS: High amounts of long-wavelength red light emitted from CRTs might play an important role in induction of photosensitive seizures in "Pokemon" incident.

Adolescent↗
PubMed1984

Time course of visual information utilization during fixations in reading.

College students read short texts from a cathode-ray tube as their eye movements were being monitored. During selected fixations, the text was briefly masked and then it reappeared with one word changed. Subjects often were unaware that the word had changed. Sometimes they reported seeing the first presented word, sometimes the second presented word, and sometimes both. When only one word was reported, two factors were found to determine which one it was: the length of time a word was present during the fixation and the predictability of a word in its context. The results suggested that visual information is utilized for reading at a crucial period during the fixation and that this crucial period can occur at different times on different fixations. The pattern of responses suggested that the first letter of a word is not utilized before other letters and that letters are not scanned from left to right during a fixation.

Adult↗
PubMed1984

Manipulation of stimulus onset delay in reading: evidence for parallel programming of saccades.

On-line eye movement recording of 12 subjects who read short stories on a cathode ray tube enabled a test of direct control and preprogramming models of eye movements in reading. Contingent upon eye position, a mask was displayed in place of the letters in central vision after each saccade, delaying the onset of the stimulus in each eye fixation. The duration of the delay was manipulated in fixed or randomized blocks. Although the length of the delay strongly affected the duration of the fixations, there was no difference due to the conditions of delay manipulation, indicating that fixation duration is under direct control. However, not all fixations were lengthened by the period of the delay. Some ended while the mask was still present, suggesting they had been preprogrammed. But these "anticipation" eye movements could not have been completely determined before the fixation was processed because their fixation durations and saccade lengths were affected by the spatial extent of the mask, which varied randomly. Neither preprogramming nor existing serial direct control models of eye guidance can adequately account for these data. Instead, a model with direct control and parallel programming of saccades is proposed to explain the data and eye movements in reading in general.

Adult↗
PubMed1985

Some temporal characteristics of processing during reading.

College students read passages displayed on a cathode-ray tube as their eye movements were being monitored. During occasional fixations, all letters to the left of the directly fixated letter or all letters more than four to the right of the fixated letter were replaced by other letters. This replacement occurred either for only the first 100 ms of the fixation or only after the first 100 ms of the fixation. The eye movement data indicated that the eyes can respond to change in the visual stimulus within less than 100 ms and to orthographic irregularity in the text within less than 160 ms. No evidence was found for a left-to-right attentional scan during a fixation. The results were interpreted within the framework of a chronology of processing events occurring during a fixation in reading.

Attention↗
PubMed1986

Depth perception as a function of motion parallax and absolute-distance information.

The results of three experiments demonstrated that the visual system calibrates motion parallax according to absolute-distance information in processing depth. The parallax was created by yoking the relative movement of random dots displayed on a cathode-ray tube to the movements of the head. In Experiment 1, at viewing distances of 40 cm and 80 cm, observers reported the apparent depth produced by motion parallax equivalent to a binocular disparity of 0.47 degree. The mean apparent depth at 80 cm was 2.6 times larger than at 40 cm. In Experiment 2, again at viewing distances of 40 cm and 80 cm, observers adjusted the extent of parallax so that the apparent depth was 7.0 cm. The mean extent of parallax at 80 cm was 31% of that at 40 cm. In Experiment 3, distances ranged from 40 cm to 320 cm, and a wide range of parallax was used. As distance and parallax increased, the perception of a rigid three-dimensional surface was accompanied by rocking motion; perception of depth was replaced by perception of motion in some trials at 320 cm. Moreover, the mean apparent depths were proportional to the viewing distance at 40 cm and 80 cm but not at 160 cm and 320 cm.

Cues↗
PubMed1998

Adaptive internal model of intrinsic kinematics involved in learning an aiming task.

The elbow-joint angle and the shoulder-joint angle of participants aiming at targets were multiplied in an experiment that used a position-recording system and a cathode-ray tube screen. The linear transformation in joint angles (intrinsic coordinates) corresponded to a nonlinear transformation between the hand coordinates and the screen coordinates (extrinsic coordinates). We examined whether participants could learn this transformation in the intrinsic coordinates or in the extrinsic coordinates by investigating intermanual (between-hands) transfer under an intrinsically consistent condition and an extrinsically consistent condition. Positive intermanual transfer was observed in the former condition but not in the latter condition. Results suggest that participants can learn the linear transformation in joint angles under the intrinsic coordinates and that the central nervous system adaptively represents the intrinsic kinematics.

Adaptation, Psychological↗