Ambient Light Levels for Radiological Soft Copy Viewing: A Multi-Site Comparison

The purpose of the study was to investigate ambient light levels in three environments where radiological images are viewed, including radiologist reporting areas, radiographer viewing stations, and radiographer wards to compare recorded levels with recommendations and consider possible causal agents for excessive levels. Ambient lighting at 30 cm and 100 cm from the display device was measured with a calibrated Nuclear Associates 07-621 photometer (Hicksville, New York). Two hospitals participated in this investigation and all monitors (n=89) used within each hospital for the viewing/reporting of radiological images were included. Values obtained were compared with recommended levels and comparisons were made between hospitals for the same viewing area using the Mann Whitney-U non-parametric statistical test. Of the monitors studied, 74 percent adhered to the World Health Organization recommended maximum of 100 lux at 30 cm from the image, while compliance fell to 45 percent when values recorded at 100 cm were compared to the European Commission guideline maximum of 50 lux. Most of the monitors with excessive ambient lighting were located in ward areas, with one hospital demonstrating 7 percent compliance in this environment. Statistical differences were shown between hospitals for radiology (p<0.0001) and ward (p<0.01) areas. It is clear from the data provided that planning is required in the positioning of display devices with careful consideration of artificial and natural lighting if diagnostic efficacy is not to be compromised. Ambient light measurement techniques require standardization.