Viewing conditions for diagnostic images in three major Dublin hospitals: a comparison with WHO and CEC recommendations.

Accurate interpretation of X-ray images is dependent on image viewing conditions. A recent study in Ireland demonstrated that even with the advent of digital departments the majority of images are still viewed using viewing boxes. This investigation aimed to measure average viewing box brightness, percentage uniformity and ambient light levels in radiology and radiographer viewing areas and wards within three major Dublin hospitals. The results were compared with published recommendations by the World Health Organization and Commission of the European Communities. Following analysis of more than 4650 measurements, it was shown that mean values for average viewing box brightness for all departments failed to achieve recommended levels. Only one third of areas met the most lenient guideline for percentage uniformity. Ambient lighting was shown to be unacceptable for ward areas. For all three parameters, radiology areas generally fared best, with wards gaining the poorest scores. Following a 3 min cleaning regimen of viewing boxes, the average brightness and percentage uniformity were improved in 100% and 80%, respectively, of viewing boxes, but average brightness values remained below recommended levels. The importance of comprehensive quality assurance programmes for viewing boxes has been highlighted so that visualization of images is not reduced to sub-optimal levels. The need for consistent and more informative recommendations has been emphasized.