The World is Flat: LCD Technology Delivers the Visual Edge

Twitter icon
Facebook icon
LinkedIn icon
e-mail icon
Google icon
The tools for diagnostic radiology and its interpretation have undergone a sea change over the past couple decades. The durable light-box alternator has given way to the desktop workstation and soft-copy interpretation, either on cathode ray tube (CRT) or flat-panel liquid crystal displays (LCDs).

The introduction of LCD panel monitors in the medical marketplace has thoroughly supplanted CRT-based displays with a surge in deployment, in part due to the reduced footprint, easier quality assurance, and longer lifetime of LCD technology.

A combination of liquid-crystal processes tuned for medical applications, greater noise reduction as well as more uniform, stable and powerful backlit illumination have eliminated many of the previous drawbacks of LCDs.

The physical characteristics and quality of display are of great import for any diagnostic imaging interpretation. Luminance, contrast, resolution, sharpness and uniformity across the digital display are critical for diagnostic-quality. High spatial requirements necessary to display subtle gradations in shading, and the very small details within that shading, are of particular importance to interpreting clinicians.

Flat is where it’s at

When it comes to soft-copy interpretation of digital images in the reading room trenches, flat-panel LCD monitors trump CRTs for a host of economic and ergonomic reasons.

Radiology is moving away from CRT monitors for a variety of reasons. CRTs typically have a low luminance, approximately 300 candelas per square meter (cd/m2); requiring low ambient light in reading rooms that makes comparisons with light-box based prior images difficult.

In addition, CRTs have a life expectancy of approximately 30,000 hours (about three years of daily clinical use); and they degrade over time, requiring their replacement rather than repair. Because CRTs require the screen to be constantly refreshed due to phosphor stimulation decay, eye fatigue is also a factor for radiologists interpreting digital images on this technology.

From a deployment perspective, CRTs for diagnostic interpretation are heavy (approximately 40 pounds), have a large footprint and produce a significant heat output—sometimes resulting in the requirement of additional air conditioning for a reading room. As such, LCDs have rapidly become the display of choice for interpreting radiologists.

“We first had CRTs when we started our digital interpretation,” says Stamatia Destounis, MD, with Elizabeth Wende Breast Care in Rochester, N.Y. “When we moved to flat-panel [LCD] monitors, the image quality improved. The black was black; the differentiation in the grays and the whites for the dense tissue was much easier for our eyes and also for interpretation.”

Destounis offers some ergonomic pearls garnered from her experience with digital interpretation. “You should position yourself no further than an arm’s length away from the monitors, and we’ve found a slight angle between displays in a two-panel setup reduces incidental lighting from one monitor to the other,” she says. “Also, a 15- to 20-degree angle below eye level for the viewing area [where the top of the monitor is at eye level] really helps improve visualization and reduce strain.”

Mass market medical monitors?

As the consumer market for computer game playing has heated up over the past decade, so has the demand for high-quality, high-resolution displays on which to engage these applications.

“The very important question that many departments are asking today, however, is whether commercial off-the-shelf [COTS] color displays are adequate or are high-performance medical-grade color displays required,” writes Elizabeth Krupinksi, PhD, from University Medical Center in Tucson, Ariz., in an article published online in September 2008 in the Journal of Digital Imaging.

According to Joe Moore, chief information officer at Radiology Consultants of Iowa (RCI) in Cedar Rapids, the rapid quality and resolution gains in COTS displays are worth tracking as they begin to approach medical-grade quality.

“Video cards, in particular, have really come along fast,” he notes. “Graphic processing units are now right on the cards as well as an increased amount of memory.”

Krupinski, who pitted COTS displays against medical-grade displays in her lab, found that the daily demands for diagnostic quality could grind down these lower-priced monitors.

“Although COTS color displays may be less expensive to purchase, the medical-grade displays are generally more stable over time in terms of maintaining consistent levels of backlighting and thus luminance levels,” she writes. “The results of this study suggest that after just one year of use, the COTS display may degrade enough to negatively impact diagnostic and visual search performance.

Clearly, COTS displays are continually improving, but care should still be taken when considering whether to purchase medical-grade versus COTS color displays for primary diagnostic interpretation.”

Reaching for real estate

“The most substantial investment in fitting out individual workstations, one with significant effects on productivity and accuracy, is the selection of monitors and monitor configurations,” writes Khan M. Siddiqui, MD, and his colleagues from the University of Maryland School of Medicine in the June issue of the Journal of the American College of Radiology.

An area that has seen some interest in the diagnostic interpretation arena is the availability of larger-screen, high-resolution LCD technology. At RCI, the standard setup for radiologists in the practice is four flat-panel displays, to see current and prior images simultaneously.

He investigated the latest offerings in large-screen, 4-megapixel (MP), dual-video input displays during the 2008 Radiological Society of North America (RSNA) conference, and was intrigued by the capability to display full-size, full-resolution images side-by-side on the same screen.

“A couple advantages to the large-screen LCD monitors are space, of course, and perhaps cost,” Moore notes. “A single 4-MP display will probably be more cost-effective than two 2-MP displays, both in terms of price and maintenance.”

However, he plans on holding out for the next generation of 10-MP displays, that can be split into two 5MP displays so that digital mammography can be interpreted on the same desktop setup.

Also, he plans on phasing in new displays as older monitors need replacing—rather than wholesale replacement.

However, when the next new display is available on the market, he will be giving it careful scrutiny.

“Our most expensive and valuable asset is our doctors,” Moore notes. “Our objective is to provide them the best tools possible to enhance their professional skills.”