Rationale and Objectives
Recent research has provided evidence that in reading rooms equipped with liquid crystal displays (LCDs), a measured increase of ambient lighting may improve clinicians’ detection performance. In agreement with this research, the American College of Radiology (ACR) has recommended a moderate increase of ambient lighting in mammography reading rooms. This study was designed to examine the effect of a controlled increase of ambient lighting in mammography reading rooms on the diagnostic performance of breast imaging radiologists.
Materials and Methods
Four breast imaging radiologists read 86 mammograms (43 containing subtle cancerous masses and 43 normal) under low ( E = 1 lux) and elevated ( E = 50 lux) ambient lighting levels on a Digital Imaging and Communications in Medicine–calibrated, medical-grade LCD. Radiologists were asked to identify cancerous masses and to rate their detection confidence. Observer areas under the curve (AUCs) were calculated using a receiver-operating characteristic analysis of fully paired results. Additionally, average observer selection times under both ambient lighting levels were determined.
Results
Average radiologist AUCs decreased with elevated ambient lighting (0.78 ± 0.03 to 0.72 ± 0.04). Observer performance differences, however, were of the same order of magnitude as interobserver variability and were not statistically significant. Average selection times under increased ambient lighting remained constant or decreased, with the greatest decrease occurring for false-positive (20.4 ± 18.9 to 14.4 ± 9.6 seconds) and true-positive (18.0 ± 13.8 to 12.9 ± 9.4 seconds) selections.
Conclusion
The results agree with those of previous studies in that observer performance differences under a controlled increase of ambient lighting are not statistically significant. On the basis of these findings and ACR guidelines, a moderate increase of ambient lighting in mammography reading rooms is still suggested, but further research with additional cases and observers should be considered.
The introduction of liquid crystal displays (LCDs) to diagnostic radiology has necessitated the re-evaluation of an optimum reading room environment. Although many reading room environmental conditions may affect observer performance, ambient lighting is known to be an especially important aspect of radiologist detection performance and comfort. In film-based mammography reading rooms, ambient lighting has typically been kept at a minimal level to maintain perceived image contrast . At this lighting level, however, a reader’s pupils will contract and dilate as the visual focus shifts between reading the high-luminance image ( L adp ) and the lower luminance surrounding background ( L s ). This pupillary action may lead to radiologist fatigue and result in the degradation of diagnostic performance . However, a moderate increase of ambient lighting, such that L s is close to L adp , might reduce pupillary action and potentially improve radiologist comfort and detection performance.
Modern calibration-capable, medical-grade LCDs, with intrinsically low diffuse reflection coefficients and high luminance ratios, may permit moderately elevated ambient lighting levels without a loss of image quality . Recent research has provided initial theoretical and physical evidence that a measured increase of reading room illuminance might lead to improved observer performance . In view of these findings, the American College of Radiology (ACR) has issued guidelines encouraging a moderate increase of ambient lighting levels in mammography reading rooms .
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Materials and methods
Image Data
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Illuminance Levels
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Display System
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Observer Study
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Performance Evaluation
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Results
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Discussion
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Conclusion
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Acknowledgments
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