Color is the biggest trend in medical monitors today and the costs may surprise you, but size and grade are also receiving attention.
|Courtesy of NEC|
Michael J. Flynn, PhD, who handles radiology research for the Henry Ford Health System in Detroit, has been involved with PACS for years and has a special interest in displays. He has contributed to the display quality assessment report put out by the American Association of Physicists in Medicine and worked with the Institution of Engineering and Technology on a recent report covering display quality. Yet he was surprised to learn that the cost differential between a medical-grade grayscale monitor and a color version was less than 10%.
According to a representative from NEC Display Solutions of America, located in Itasca, Ill, the difference between the company’s 3-megapixel black-and-white monitor and the 3-megapixel color monitor is about 5%—or $200. Flynn’s reaction was to rethink future acquisitions, saying, “Our next round, we probably will have to look at whether we’ll just start buying color monitors.”
It’s a strategy many facilities are considering as monitors are upgraded throughout their systems, and cost is not the only driver. As the price has come down on color medical-grade monitors, the quality has gone up. “So, as people are buying new installations, they are saying, ?Well, if I can have color with the same performance as the grayscale, why not go color?'” said Stan Swiderski, business development manager for professional medical displays at NEC.
Generally, the advantages of a color display outweigh the disadvantages. This is not necessarily the case for size and grade, however, which encounter limitations when used for diagnostic purposes. Even so, larger monitors receive a lot of attention for their coolness factor, while consumer-grade monitors are considered because of their lower cost.
Ultimately, the intended use of the monitor should influence its selection. Diagnostic and clinical applications have different requirements for characteristics, such as resolution, pixel pitch, brightness, and color, so it is important to match the monitor function with its capabilities.
Monitors Come Through with Flying Colors
“Radiology is inherently a grayscale modality, so color is probably never necessary, but it does add a certain dimension of facility to reading exams,” said Elizabeth Krupinski, PhD, professor and vice chair of research in the Department of Radiology at the University of Arizona in Tucson.
Some modalities, however, have incorporated color into the images so usefully that to read them on a grayscale would be challenging. Doppler ultrasound and nuclear medicine fall into this category. In other modalities, color adds a nice touch, whether pseudocolor in actual images or colors used in annotation.
“We as humans just seem to gravitate to color images. It’s more of a natural thing,” Swiderski said. He notes there is software in development that will use color more prevalently in diagnosis, offering computer-aided diagnostics as an example. “Color monitors help to future proof your installation,” Swiderski said.
This is different than the situation in the past. “Color monitors, historically going back a few years, were able to achieve a brightness of only 150, 170, or 190 candelas,” said Bill Greenblatt, vice president of sales and marketing for Quest International Inc, Irvine, Calif. Grayscale monitors are often calibrated to a luminance of 400 to 500 candelas. So color monitors traditionally lacked the brightness required for diagnostic purposes. That has changed.
“In the last several years, we have experienced a very positive shift in that the color diagnostic displays are easily able to achieve luminance levels similar to the grayscale—that of 400 candelas. So now you’re able to really compare, if you will, apples with apples,” Greenblatt said.
The improved brightness of the color monitors means they can be used for grayscale applications as well as color. The increasing prevalence of color in imaging software means physicians want, and even need, to use the color option more frequently. It therefore becomes a more valuable investment to buy color monitors rather than grayscale, particularly as the prices of both types of monitor converge.
“Because today’s color monitors can be used for both grayscale and color images, it boils down to an overall lower cost within the facility. Now you don’t need x number of grayscale monitors for black-and-white images and x number of color monitors for your color images,” Greenblatt said.
The use of multitasking color monitors for all applications can also impact radiologist productivity and footprint. Physicians don’t have to switch workstations to view color images, and with multitasking monitors, not as many workstations are needed.
|Courtesy of Quest International|
Certain applications, however, do still require grayscale monitors. Mammography, for instance, requires a 5-megapixel monitor. “There are no color displays available in the 5-megapixel size,” Swiderski said. In addition, though the brightness of color monitors is adequate at the calibrated level of 400 candelas, grayscale monitors have the potential to be much brighter, with maximum luminance values over 1,000 candelas; color remains below this level, which means its life may be shorter.
“Our life on a color monitor right now is about 5 years. But typically after 5 years, you’re changing the displays anyway for other reasons, such as technology innovations,” Swiderski said.
Continued advances, though, are likely to address these disadvantages. “I think we’re headed toward a point where we will see only color products on the market. I don’t think industry is going to be able to support the specialized fabrication lines needed to continue to produce small volumes of monochrome monitors,” Flynn said.
Sizing Up Monitors
Unlike the ease of color, size may not be so compatible with human ergonomics, limiting how large diagnostic displays can be. Today’s diagnostic monitors top out at 55 inches, according to Greenblatt; clinical monitors get even larger. But for diagnostics, the 30-inch widescreen is a popular size.
“If a person is sitting at the normal working distance at a workstation reading, the field of view you want to present the image in really can’t be much larger than about the 20- or 22-inch diagonal size. If you present an image larger than that, then the peripheral portions of the scene are outside the view that the human eye can respond to,” Flynn said.
However, Krupinski agrees that size is limited by ergonomics. “There’s a point where the bigger the monitor gets, the farther back you have to sit, but if you move back too far, then you lose that resolution,” Krupinski said.
The larger monitors, however, offer the advantage of greater real estate for images. “As long as it has the spatial resolution, you could put two chest images on the same monitor, side by side,” said Krupinski, noting it permits the consistent display of two different images.
A 30-inch monitor can display images in the same format as two 20-inch monitors with a 4:3 aspect. This means the radiologist must scan only one monitor rather than move his gaze from monitor to monitor. “You reduce, in a sense, the physical strain on the body, and it gives you more real estate,” Krupinski said.
Color is also more consistent, since two monitors will need to be color matched. “Radiologists definitely want the monitors to be color matched, and they don’t want anything that’s going to distract them from the image, like a bezel,” Swiderski said.
With a 30-inch diagonal, a radiologist can replace the two-monitor configuration with just one large screen. This is more cost-effective. “To give you an example, the 30-inch 4-megapixel costs about $4,000. The two 2-megapixel 21-inch [configuration] would cost in the neighborhood of $6,000 to $7,000. So it’s actually less cost for a 30-inch, but you’re getting less lifetime and less brightness,” Swiderski said.
NEC’s 4-megapixel, 30-inch monitor is calibrated at 200 candelas, more than the 172 candelas required by the American College of Radiology but less than the 400 candelas on the 2-megapixel, 21-inch display.
In addition, a one-monitor configuration for diagnostics eliminates the built-in backup inherent to a two-monitor configuration. “I don’t think we’ve had these bigger monitors around long enough to notice if there are any different quality control issues than there were with the monitors that have been standard for a number of years now. But given the technological challenges and TFTs [thin-film transistors] that the monitors themselves are made out of, at some point I would think that the more pixels you get, the more likely it is they are going to die on you,” Krupinski said.
A bigger question than the impact of size, however, is the impact of commercial off-the-shelf options, referred to as COTS. “The monitors that you can get just off the shelf at a regular computer store are really getting up to the quality that a lot of people find sufficient for certain types of radiological exams, and they are a lot less cost than those high-performance, medical-grade monitors,” Krupinski said.
She authored a study in which the diagnostic accuracy of radiologists viewing clinical images on a top-of-the-line medical-grade monitor was compared to that when reading on a top-of-the-line COTS color display. The work concluded, “Medical-grade color displays at 1-year-old yield better diagnostic and search efficiency than COTS color displays.”1
“With the medical-grade monitors, you’re buying a higher quality product. They’ve gone through a lot more rigorous testing and development. They physically have higher spatial resolution, higher contrast resolution, and less noise than off-the-shelf monitors. And their lifetime is probably going to be longer,” Krupinski said. These advantages can justify the extra expense of a medical-grade monitor. IE
The quality control technologies used to maintain luminance levels of monitors provide further justification, as well as protection from litigation. “Being able to maintain a given level of brightness over a period of time is something that the majority, if not all, of the medical-grade displays provide for today, but the majority of the commercial off-the-shelf LCDs do not offer that capability. They’ll just start degrading,” Greenblatt said.
Luminance can also vary during one session with COTS displays. “COTS LCDs typically take a long time to stabilize their brightness. Usually, it’s anywhere from 60 to 90 minutes before their luminance reaches a level that is maintained,” Greenblatt said. Medical-grade displays, by contrast, achieve the calibrated brightness within minutes, if not immediately, and as the backlights warm up, internal electronics start decreasing the backlight brightness to maintain the calibrated level.
Even as COTS quality increases to meet the brightness, resolution, and other requirements needed for diagnostic purposes, the level of quality control remains a concern. “Even though the resolution might be there and they’re brighter and bigger and everything else, I’m not sure there is enough quality control for the higher resolution images that we have to look at,” Krupinski said.
COTS machines, however, can prove useful as clinical tools. Their quality can be high enough for secondary functions, such as reviews, physician/patient consultations, and navigation, permitting some cost savings. “I think what is happening is the economy is getting squeezed in every direction, especially recently, and more and more people are trying to cut corners,” Swiderski said.
Diagnostic monitors are not the place to do it, an opinion that most in the industry share. “I would say 99% of all the radiology departments at least use a medical-grade type of display for primary reads,” Swiderski said. As they continue to advance, this is likely to remain the case.
Renee Diiulio is a contributing writer for Axis Imaging News.
- Krupinski EA. Medical-grade vs off-the-shelf color displays: influence on observer performance and visual search. J Digit Imaging. 2009;22:363-368. Epub September 3, 2008.