P024] The enlightening of radiologists

Abstract

Purpose The working environment for radiologists typically consists of dark rooms in order to increase image contrast. From an ergonomic viewpoint, dark rooms are far from ideal. Darkness is likely to cause fatigue, loss of concentration and thus a potential degradation of diagnostic accuracy. Also, a low screen luminance requires a rigorously controlled ambient illuminance in order to avoid contrast loss due to fluctuating reflections. The purpose of this talk is to examine the scientific reasons for using dark reading rooms. Are they indisputable or do old habits simply die hard? By using state-of-the-art displays – is it possible that an increase in light could also be beneficial to image quality as well as ergonomic conditions? Methods Display contrast was determined by calculating the number of just noticeable differences (jnd) for several display luminance settings. Since the jnd is based on a limited number of biological processes, effects caused by absolute luminance level, eye adaptation, luminance range and visual acuity were also examined. Results For a constant luminance ratio, the contrast increased with luminance. An increase in black level allowed for an increase in ambient light, i.e. less dark reading rooms. By using a high maximum luminance and a reduced luminance range, bright reading rooms could be used without compromising image quality. Unfortunately, most standards and guidelines require a minimum luminance range, forcing the maximum luminance to be higher than technically achievable when increasing the minimum luminance. A reduced luminance range lowers the contrast but can also have positive effects since the human visual system performs better for small differences in luminance. An increased black level causes the eye to always work in photopic mode where visual acuity is higher and small details are more easily detected. Conclusions With bright medical displays available, it is theoretically possible to use higher luminance settings in brighter rooms while maintaining – or increasing – image quality. In brighter rooms, radiologists will be able to work in normal office light and relatively large fluctuations in ambient lighting can also be allowed without any significant reductions in image contrast.