Amarpreet Singh Chawla MS, Presenter: Nothing to Disclose

Ehsan Samei PhD, Abstract Co-Author: Nothing to Disclose

To develop a new approach based on the adaptation characteristics of the human visual system to optimize the ambient lighting conditions of radiology reading rooms.

Currently, the ambient lighting levels in radiology reading rooms are determined based on the reflection properties of display devices per recent TG18 standard. This approach necessitates notable variations in the adaptation state of the radiologist’s eyes when moving the gaze from the display to the surround surfaces. This variation is one source of visual fatigue and thus its minimization can potentially reduce eye fatigue. As a first step towards this goal, we developed a computational model to determine a mean adaptation luminance level, ξ, corresponding to the mean pupil size when viewing a typical medical image. ξ values were calculated for different room lighting conditions and calibration settings of soft-copy display devices. Those values were then compared with measured luminance values on typical surfaces in a reading room, ζ.

The diffuse reflection coefficient, Σ, of surfaces typically used in radiology reading rooms are in the 0.01-0.32 1/sr range. For typical ambient lighting illumination of 1-80 lux, these surfaces reflect ζ luminance values in the 0.01-25 cd/m² range. Under similar lighting conditions (assuming a typical display Σ of 0.01-0.02 1/sr), ξ on a DICOM calibrated monitor with maximum luminance of 300 to 600 cd/m² vary between 20 to ~45 cd/m². These results suggest that a careful combination of room surfaces with high Σ and proper illumination can be used to achieve ζ values close to ξ. This will minimize variation in visual adaptation (and thus eye fatigue) while still maintaining compliance with the TG18 standard.

Current standards do not take into account variations in visual adaptation for optimal setup of medical imaging reading rooms. New LCDs with high maximum luminance and luminance ratios enable a new approach to setting up radiology reading rooms such that variation in adaptation level can be minimized without undue effect on contrast in dark regions of the image, thus minimizing eye fatigue.

Chawla, A, Samei, E, A New Adaptation-based Approach for Optimizing the Ambient Light Conditions in Radiology Reading Rooms.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4413341.html