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Newer display technology finds growing support as cheaper versions make the grade
By: Merlina Trevino and Douglas Page
How best to display medical images remained an issue at this year's SCAR conference. Research presentations suggested, however, that consumer-grade LCD monitors, including those with color, are ready to enlarge their role in the imaging marketplace.
One study found no significant difference between consumer-grade color flat-panel monitors and medical-grade high-luminance monochrome CRT monitors for primary diagnosis of abdominopelvic CT exams. Another presentation explained how the color available on LCD monitors may actually be superior to black-and-white displays in high-grade CRT monitors for reading gray-scale images. A third study found 3-megapixel LCDs equivalent to 5-megapixel CRTs in their ability to display lung nodules.
"Although medical-grade display systems may be necessary for primary diagnosis of radiographs, consumer-grade flat-panel monitors and videocards that cost less and support the display of color images probably suffice for primary diagnosis of CT exams," said Dr. David Hirschorn, a clinical fellow in informatics at Massachusetts General Hospital.
While 70% of all exams are radiographs, the assumption that primary diagnosis images from other modalities should be viewed on the same display system is a costly one, Hirschorn said. A medical-grade dual-monitor workstation can cost from $5000 to $30,000, but $2500 can buy a pair of 19-inch consumer-grade color flat-panel monitors operating at resolutions up to 2 megapixels.
The similarity in diagnostic quality applies even to subtle findings. In Hirschorn's study, differences either did not matter or were overcome by the radiologist's ability to adjust the window and level of the images as desired.
"As the use of color in radiologic imaging grows in importance, so does the need to display color images," he said.
Color is commonly used in Doppler ultrasound imaging and nuclear medicine. Newer techniques such as functional MR imaging and PET/CT fusion require color displays as well.
"At this time, medical-grade monitors suitable for radiography cannot display color," Hirschorn said. "The validation of consumer-grade color monitors for primary diagnosis of nonradiographic studies can have a huge impact on the ability of PACS to support the display of color images."
The performance of LCD monitors versus CRT monitors is a long-standing debate in radiology informatics circles, and it appears to be tipping in favor of the LCDs. Many characteristics such as resolution, display noise, gray-scale presentation, and service make the purchase of an LCD monitor more attractive, said Michael J. Flynn, Ph.D., senior staff physicist at the Henry Ford Health System in Detroit, in a SCAR University presentation.
Henry Ford has removed all of its CRT systems and now employs 530 single 1-megapixel color LCD stations, 20 dual 1-megapixel LCD stations, and 10 stations with 1-megapixel color and 2-megapixel monochrome LCDs.
Flynn also tackled the issue of displaying gray-scale images on color monitors. CRT color technology is not really up to the task of presenting high-resolution images in comparison with monochrome CRT devices, he said. New color LCD monitors, on the other hand, have high brightness and can produce superior quality monochrome presentations.
Generally, color manipulation allows better precision for gray-scale calibration of color LCD monitors, according to Flynn. By adjusting the red, green, and blue values, radiologists can achieve precise gray-scale calibration.
BEAUTY CONTEST
Research conducted at the Mayo Clinic in Rochester, MN, determined that the performance of 3-megapixel LCD monitors matches that of 5-megapixel CRT monitors in detecting subtle interstitial lung disease.
Radiology departments are increasingly purchasing LCD rather than CRT monitors, despite a dearth of literature comparing their performance, said Steve Langer, Ph.D., senior associate consultant in diagnostic imaging at Mayo.
"The market is on a cusp," he said. "We're moving toward the broader use of LCDs."
To compare the two display types, Langer and colleagues designed a study in which five observers viewed a total of 310 images on each display: 230 were abnormal interstitial lung disease cases, and 80 were normal. The images had to be chosen carefully because the researchers wanted to avoid cases with obvious results, in which the quality of the monitor would not have made a difference.
"Our goal was to find subtle distinguishing features between these two different displays," said study coauthor, Dr. Brian J. Bartholmai, an electronic imaging fellow at Mayo's Radiology Informatics Laboratory.
Using chest computed radiography images from 1997 to 2003 with CT-proven disease, the researchers could pull CRs with very subtle indications of interstitial lung disease. They had a large pool of acceptable cases because the disease is fairly common, but indications are often subtle.
"There aren't many radiology cases that are confirmed and yet subtle," Bartholmai said.
Langer and colleagues chose to use the manufacturer's full display recommendations for both LCD and CRT. Choosing to calibrate one type with the other could eliminate the potential strengths of either display. Calibrating both monitors' luminance settings, for example, might not allow LCD monitors their full range.
The researchers measured outcomes in terms of observer accuracy, time spent on task, and diagnosis confidence. The specificity for both monitors was above 96%, Langer said. There were no significant differences in sensitivity.
In time spent on task, neither monitor increased or decreased interpretation time. Rather, times always decreased with the second monitor used, whether observers read their second cases on a CRT or LCD.
"Within 80% power, the efficacy of a 3-megapixel LCD is not worse than a 5-megapixel CRT as measured by intraobserver sensitivity/specificity," Langer said.
He presented the results at the third SCAR Research and Development Committee Symposium. During a discussion following, the question of a "beauty contest" was raised. Langer responded that his group didn't have a formal answer to that question but did notice anecdotally that older radiologists tended to prefer the CRT and younger physicians preferred the LCD.
A member of the audience asked Langer what his facility was purchasing.
"We're buying LCDs," he said.
Michael Flynn, Ph.D., senior staff physicist at the Henry Ford Health System in Detroit, explains the characteristics of color LCD monitors. Their high brightness can produce superior quality monochrome images, he said.
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