The effect of increased ambient lighting on detection accuracy in uniform and anatomical backgrounds
Under typical dark conditions found in reading rooms, a reader's pupils will contract and dilate as the visual focus intermittently shifts between the high luminance monitor and the darker background wall, resulting in increased visual fatigue and the degradation of diagnostic performance. A controlled increase of ambient lighting may, however, minimize these visual adjustments and potentially improve reader comfort and accuracy. This paper details results from two psychophysical studies designed to determine the effect of a controlled ambient lighting increase on observer detection of subtle objects and lesions viewed on a DICOM-calibrated medical-grade LCD. The first study examined the effect of increased ambient lighting on detection of subtle objects embedded within a uniform background, while the second study examined observer detection performance of subtle cancerous lesions in mammograms and chest radiographs. In both studies, observers were presented with images under a dark room condition (1 lux) and an increased room illuminance level (50 lux) for which the luminance level of the diffusely reflected light from the background wall was approximately equal to that of the displayed image. The display was calibrated to an effective luminance ratio of 409 for both lighting conditions. Observer detection performance under each room illuminance condition was then compared. Identification of subtle objects embedded within the uniform background improved from 59% to 67%, while detection time decreased slightly with additional illuminance. An ROC analysis of the anatomical image results revealed that observer AUC values remained constant while detection time decreased under increased illuminance. The results provide evidence that an ambient lighting increase may be possible without compromising diagnostic efficacy.
