Use of a Human Visual System Model to Predict Observer Performance with CRT vs LCD Display of Images

Abstract

This Project evaluated a human visual system model (JNDmetrix) based on just noticeable difference (JND) and frequency-channel vision-modeling principles to assess whether a Cathode ray tube (CRT) or a liquid crystal display (LCD) monochrome display monitor would yield better observer performance in radiographic interpretation. Key physical characteristics, such as veiling glare and modulation transfer function (MTF) of the CRT and LCD were measured. Regions of interest from mammographic images with masses of different contrast levels were shown once on each display to six radiologists using a counterbalanced presentation order. The images were analyzed using the JNDmetrix model. Performance as measured by receiver operating characteristic (ROC) analysis was significantly better overall on the LCD display (P = 0.0120). The JNDmetrix model predicted the result (P = 0.0046) and correlation between human and computer observers was high (r 2 (quadratic) = 0.997). The results suggest that observer performance with LCD displays is superior to CRT viewing, at least for on-axis viewing.KEY WORDS: Vision model, observer performance, digital display A LTHOUGH PACS (picture archiving and communication systems) and teleradiology have changed the practice of radiology quite dramatically over the past number of years, there are still many changes taking place in the digital reading room. 1-3 One aspect that seems to evolve continuously is the display. 4,5 Although early investigations tended to focus on how many monitors were required in the digital reading environment and what resolution was required, 5 a critical issue today is whether flat-panel liquid crystal displays (LCDs) are more suitable for primary diagnostic reading than the more traditional CRT (cathode ray tube) display. 6,7 In many respects, the LCD has performance characteristics that exceed those of the CRT. 8,9 The MTF (modulation transfer function) of an LCD is essentially isotropic, whereas the MTF of a CRT is non-isotropic. At the highest digitally addressable spatial frequency along the CRT scanline in the horizontal direction, the value is usually only 10% to 20%. In the vertical direction the MTF at twice the line frequency is closer to 30% to 40%. 8,9 The result is that, for the CRT, more than half the contrast modulation is lost at the highest spatial frequencies, but this degradation does not occur with the LCD. Practically speaking, this could mean degradation of highfrequency lesions in radiographic images such as microcalcifications in mammograms, resulting in reduced detection performance.

Usability of liquid crystal displays for research in the temporal characteristics of perception and attention

“…It is possible that the higher peak of luminance in the raster scan CRT display increased mask intensity, relative to the other two monitors, thereby resulting in the greater metacontrast-masking effect. Another possibility is that clarity of the stimuli was related to a stronger masking effect in the raster scan CRT display, because the CRT display produced blurry images, relative to the LCD display (Krupinski et al, 2004), resulting in a greater effect of contour proximity (Alpern, 1953) under the critical masking period.…”

“…LCDs have many advantages over raster scan CRT displays in terms of weight, volume, and electrical power consumption (Menozzi, Näpflin, & Krueger, 1999). Modern LCDs are also superior to raster scan CRT displays in several aspects of static image quality (Krupinski et al, 2004). Indeed, it has been reported that in terms of assessment of quality, LCDs provide higher quality than do raster scan CRT displays (Tourancheau, Callet, & Barba, 2008).…”

The Empirical Foundations of Teleradiology and Related Applications: A Review of the Evidence

“…Subsequently, significant developments in medical-grade display technology were started in the late 1980s and continue today. The early displays were cathode ray tube, [26][27][28] but today liquid crystal displays (LCDs) and variants such as organic light-emitting diodes are the norm in most radiology reading rooms. 29,30 Some of the key display parameters that have guided the development of these displays are directly related to the perceptual requirements of radiologists, the digital nature of the images, the complex nature of anatomic structures, and lesions in the images.…”

Comparison of Color LCD and Medical-grade Monochrome LCD Displays in Diagnostic Radiology

“…1 From the Department of Radiology, Ö rebro University Hospital, SE-701 85, Ö rebro Sweden. 2 From the Department of Radiology, Sahlgrenska University Hospital, SE-413 45, Gothenburg Sweden. 3 …”

“…This is supported by several studies. 2,3 We wished to test the null hypothesis that there is no significant difference in a calculated image quality factor between contrast-detail phantom images displayed on a consumer-grade color LCD display and a medical-grade monochrome LCD display having the same resolution. We also wished to test the null hypothesis that there is no significant difference in diagnostic image quality between clinical radiographs of the lumbar spine displayed on the same monitors.…”