Substandard PACS displays plague hospital departments

August 31, 2005

Too many physicians are using subpar workstations to view images. Only about half of all primary workstations at a major tertiary-care hospital meet current criteria for minimum luminance, according to a new study.

Too many physicians are using subpar workstations to view images. Only about half of all primary workstations at a major tertiary-care hospital meet current criteria for minimum luminance, according to a new study.

"The performance of PACS workstations is critical, yet there are many poor workstations being used clinically," said John E. Aldrich, Ph.D., head of basic sciences in the radiology department at Vancouver Hospital.

Aldrich assessed the performance of all display (primary and secondary) monitors used at his institution, measuring the maximum luminance and contrast ratio in ambient and low-light conditions, and compared the results with acceptance criteria contained in the draft report of Topic Group 18 of the American Association of Physicists in Medicine. The results were published in the Journal of Digital Imaging (Aug. 5, 2005, ePub ahead of print).

"All primary radiology workstations met the acceptance criteria for maximum luminance, but no primary or secondary system met the contrast ratio in ambient light," Aldrich said.

Fifteen of the 34 primary displays did not have a contrast ratio greater than 250:1 in the low-light conditions normally used.

For secondary displays, just over half had a luminance level in excess of 100 cd/m2, but the majority had a contrast ratio greater than 100:1 in low-light conditions.

Manufacturers often quote contrast ratios of greater than 400:1 in their workstations, but this is frequently measured under ideal conditions. In real clinical environments the contrast is often much lower because of ambient light and reflections, Aldrich said.

Aldrich said a six-month-old factory-calibrated telescopic photometer (Minolta Model LS-100) was used to measure the maximum luminance and the contrast ratio for the both primary and secondary displays used in radiology, emergency, and operation suites.

Despite the vital nature of display stations in a PACS environment, there are no recent published performance standards for these systems, he said.

"Although the areas using primary displays in our center were specifically designed for PACS use (with recessed lighting, dimmer and climate controls, and custom furniture) and we have a consistent quality control program, these simple measurements indicated that some changes to ambient lighting or display location were still required," he said.