Imaging Displays: How to Zap the Nap
Imaging display systems represent a fairly substantial investment and are a crucial element in the diagnostic process. A radiologist-friendly system and configuration can go a long way toward boosting the value and utility of an imaging display and help keep radiologists focused on the task at hand.

The challenge

Any professional who stares at a screen for a long workday can attest to the visual and mental challenge of maintaining focus on a display system. Radiologists, unfortunately, are not immune. In fact, radiologists demonstrated reduced ability to focus, increased symptoms of fatigue and oculomotor strain at the end of a day of clinical reading, according to a study published September 2010 in the Journal of American College of Radiology. Researchers reported a small, but significant, reduction in accuracy of fracture detection at the end of the workday.

Radiologists need to be aware of potential problems with fatigue and take measures to avoid fatigue, says the study’s lead author Elizabeth A. Krupinski, PhD, research professor at University of Arizona in Tucson. Krupinski and her colleagues recently completed a second study, which replicated the findings of the first. Radiologists looking for pulmonary nodules on CT exams had a degradation of approximately 5 percent in diagnostic accuracy after a long day of reading.  

Display choice and configuration can help lessen the tendency toward fatigue. “Read the American College of Radiology (ACR) guidelines for choosing a proper display and maintaining good quality assurance and quality control programs,” recommends Krupinski. The guidelines address calibration and luminance levels, which affect image quality and human factors such as fatigue.

Luminance levels that are too high can lead to eye strain, and luminance levels tend to drop over time if a display system isn’t properly calibrated. As the display gets dimmer and dimmer, image quality degrades and, without proper contrast, the radiologist may have to strain to examine the images.

Medical-grade vs. consumer-grade

It’s one of radiology’s $64,000 questions. Can a consumer-grade display provide the performance specifications necessary for radiology? It used to be a black-and-white issue as consumer systems more than five years old weren’t up to the task. Today, however, the answer isn’t quite as simple.

Medical-grade displays include key features that can mitigate concerns about fatigue and eye strain. However, [non-medical] display systems that incorporate these features may provide a good option, says Alisa Walz-Flannigan, PhD, diagnostic medical physicist at Mayo Clinic in Rochester, Minn.

On the flip side, purchasing a consumer or commercial off-the-shelf display may epitomize penny wise and pound foolish. Although off-the-shelf displays suffice for most reading situations (ultrasound, CT, MRI and general chest and bone exams), radiology departments need to ensure that the systems meet the minimum requirements of the ACR’s guidelines in terms of luminance and contrast levels, says Krupinski.

Consumer-grade displays typically cannot maintain stable luminance. “Luminance on consumer grade displays will degrade over time. We like to calibrate the system once and then do quality control,” says Walz-Flannigan. But quality control may be more cumbersome on a consumer system that does not provide remote monitoring for quality assurance as some medical display systems do.

Another critical caveat is that commercial systems are not DICOM-calibrated, which requires a software download. Mayo Clinic places a priority on better luminance uniformity and quality control tools in its diagnostic display procurement process. “These are typically available with medical-grade displays,” says Walz-Flannigan.

Ultimately, practices that opt for a consumer-grade system might save on the initial purchase, but be forced to shell out resources in terms of man-hours to configure and maintain the system.

However, not all medical-grade displays are created equally. Mayo Clinic has opted against some medical-grade displays because of their shiny panels. “They make the image glossy, creating huge specular reflections. People get good at looking around those, but that can cause fatigue,” explains Walz-Flannigan.

Resolution & ratios

Screen resolution is another factor in the decision-making process. Radiologists typically use 3 megapixel (MP) displays rather than 5 MP viewers for images other than digital mammography. Although some radiologists and gadget-happy informatics professionals might be swayed by the power of the pixels for the higher price, 5 MP display systems don’t offer much, says David S. Hirschorn, MD, director of radiology informatics at Staten Island University Hospital in New York City. “The pixels are tinier, and there are more of them, but at normal viewing distances, your eyes don’t see anything differently.”

In fact, large institutions buying viewers in bulk often purchase 2 MP displays because of the cost difference between 2 and 3 MP systems and the lack of clinically relevant differences, he says.

“Manufacturers like to advertise huge contrast ratios, such as 1,000:1 to 100,000:1, but that is not particularly helpful,” adds Walz-Flannigan. “The human eye cannot perceive information across that large of a contrast range and those ratios typically arise from making really dark blacks. Image information contained in extremely dark areas of an image might not be visible because it will be masked by ambient light. Generally, we aim for around 500:1 to 600:1 for non-mammographic displays.”

Another important consideration is viewing software and its integration with the rest of the information presented on the display. “Users are not just viewing images in isolation,” says Walz-Flannigan. Bright borders or accompanying text windows can blind a person to subtle information contained in dimmer parts of an image.

Human factors

“Unfortunately, in many hospitals, radiologists move from workstation to workstation, which means displays are not optimized for individual users,” says Krupinski. The ideal situation is for each radiologist to have his or her own workstation. Then, the workstation can be optimized for the user in terms of viewing level and angle, hanging protocols, ambient light and heat.

“Once the radiologist is in a comfortable, optimized reading environment, it will lead to less fatigue because he or she is not straining as much to adapt to the environment,” says Krupinski, who offers a final pointer. That customized configuration may be comfy, but movement can help maintain focus. “Try not to sit all day. Schedule times when you can get up and move or look away from the screen. Or, read and dictate from a standing position for a while.”

A well-planned display system may reap significant dividends. The right system and configuration can help radiologists maintain focus and accuracy, while also providing streamlined IT management.