Effect of monitor luminance and ambient light on observer performance in soft-copy reading of digital chest radiographs.
OBJECTIVE
To examine the combined effects of monitor luminance and ambient light on observer performance for detecting abnormalities in a soft-copy interpretation of digital chest radiographs.


METHODS
A total of 254 digital chest radiographs were displayed on a high-resolution cathode ray tube monitor at three luminance levels (25, 50, and 100 foot-lamberts) under three ambient light levels (0, 50, and 460 lux). Six chest radiologists reviewed each image in nine modes of combined luminance and ambient light. The observers were allowed to adjust the window width and level of the soft-copy images. The abnormalities included nodule, pneumothorax, and interstitial disease. Observer performance was analyzed in terms of the receiver operating characteristics. The observers reported their subjective level of visual fatigue with each viewing mode. A statistical test was conducted for each of the abnormalities and for fatigue score by using repeated-measures two-way analysis of variance with an interaction.


RESULTS
The detection of nodules was the only reading that was affected by the ambient light with a statistically significant difference (P <.05). Otherwise, observer performance for detecting a nodule, pneumothorax, and interstitial disease was not significantly different in the nine-mode comparison. There was no evidence that the luminance of the monitors was related to the ambient light for any of the abnormalities. The fatigue score showed a statistically significant difference due to both the luminance and ambient light.


CONCLUSIONS
When adequate window width and level are applied to soft-copy images, the primary diagnosis with chest radiographs on the monitor is unlikely to be affected under low ambient light and a monitor luminance of 25 foot-lamberts or more.
Department of Radiology, Seoul National University College of Medicine and the Institute of Radiation Medicine, SNUMRC, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea.
Jin Mo
JM
Goo
Ja-Young
JY
Choi
Jung-Gi
JG
Im
Hyun Ju
HJ
Lee
Myung Jin
MJ
Chung
Daehee
D
Han
Seong Ho
SH
Park
Jong Hyo
JH
Kim
Sang-Hee
SH
Nam
D016288:Computer Terminals; D003308:Copying Processes; D006801:Humans; D008029:Lighting; D015588:Observer Variation; D011856:Radiographic Image Enhancement; D013902:Radiography, Thoracic / Q000379:methods / Q000592:standards*