High-use flat-panel displays require conscientious QC
CHICAGO—The luminance levels of flat-panel displays can degrade over time and are affected by the utilization of the monitors, according to a team of Japanese researchers who presented their analysis in a poster presentation at the 94th annual meeting of the Radiological Society of North America (RSNA).

“To prevent medical malpractice, quality control (QC) for luminance of high-quality medical displays at PACS terminals is very important,” wrote the authors of the multi-institution study.

The team, from Nagoya City University Hospital central division of radiology, Kanazawa University School of Health Sciences, and Fujita Health University, noted that in the 4 years since the introduction of PACS, degradation can now be seen on many displays.

In the study, they investigated the correlation between the frequency of use and luminance degradation in heavily-used displays for image interpretation in the department of radiology and the less-frequently-used displays at other departments.

Their PACS (Centricity, GE Healthcare) consists of 60 terminals with 48, 3-megapixel (MP) diagnostic grayscale displays (Coronis 3MP, Barco) and 29, 2-MP (ME 203L, Totoku) monitors.

The researchers used a telescopic-type luminance meter (LS100, Konica-Minolta) and a color-display analyzer (CA210, Konica-Minolta) to measure the luminance levels of the monitors in their institution, which were assessed twice a year for a period of 4 years beginning in January 2004 through January 2008.

The displays were divided into two groups from the measurement results.

One group was the displays at the PACS workstations used for a considerable time each day in the radiology department, and the other group was display monitors that were used less frequently.

The latter included almost all displays in the medical departments other than radiology, they noted. The average cumulative hours of use for radiology displays were 144,880 hours, while those for other department displays were 2,192 hours.

“Data for degradation of luminance could be approximated by the linear function, and the inclination was -0.0063 for radiology displays and -0.0009 for other department displays, with a significant difference between the two (P < 0.01),” they wrote.

They observed that when the highest luminance became 350 candelas per meter squared (cd/m2) or less, luminance hardly recovered, even though calibration was carried out.

“In a previous study, it was confirmed that diagnostic ability fell by using displays when the highest luminance was degraded by 30 percent or more from the maximum luminance level of 500 cd/m2,” they stated.

The team’s research found that after about 20,000 hours of cumulative use, luminance had degraded to approximately 400 cd/m2.

“In frequently-used displays for image reading at the radiology department, degradation was found to be more advanced than expected,” they reported. “Exchange or repair is required for displays in which the luminance is found to be below QC limits.”