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