In order to prevent specular reflections, many monitor faceplates have features such as tiny dimples on their surface to
diffuse ambient light incident on the monitor, however, this "anti-glare" surface may also diffuse the image itself. The
purpose of the study was to determine whether the surface characteristics of monitor faceplates influence the detection of
pulmonary nodules under low and high ambient lighting conditions.
Methods and Materials
Separate observer performance studies were conducted at each of two light levels (<1 lux and >250 lux). Twelve
examining radiologists with the American Board of Radiology participated in the darker condition and eleven in the
brighter condition. All observers read on both smooth "glare" and dimpled "anti-glare" faceplates in a single lighting
condition. A counterbalanced methodology was utilized to minimise memory effects. In each reading, observers were
presented with thirty chest images in random order, of which half contained a single simulated pulmonary nodule. They
were asked to give their confidence that each image did or did not contain a nodule and to mark the suspicious location.
ROC analysis was applied to resultant data.
No statistically significant differences were seen in the trapezoidal area under the ROC curve (AUC), sensitivity,
specificity or average time per case at either light level for chest specialists or radiologists from other specialities.
The characteristics of the faceplate surfaces do not appear to affect detection of pulmonary nodules. Further work into
other image types is being conducted.
Detection of low-contrast details is highly dependent on the adaptation state of the eye. It is important therefore that the
average luminance of the observer's field of view (FOV) matches those of softcopy radiological images. This study
establishes the percentage of FOV filled by workstations at various viewing distances.
Five observers stood at viewing distances of 20, 30 and 50cm from a homogenous white surface and were instructed to
continuously focus on a fixed object at a height appropriate level. A dark indicator was held at this object and then
moved steadily until the observer could no longer perceive it in his/her peripheral vision. This was performed at 0°, 90°,
180° and 270° clockwise from the median sagittal plane. Distances were recorded, radii calculated and observer and
mean FOV areas established. These values were then compared with areas of typical high and low specification
Individual and mean FOVs were 7660, 15463 and 30075cm2 at viewing distances of 20, 30 and 50cm respectively. High
and low specification monitors with respective areas of 1576.25 and 921.25cm2 contributed between 5 to 21% and 3 to
12% respectively to the total FOV depending on observer distance. Limited inter-observer variances were noted.
Radiology workstations typically comprise between only 3 and 21% of the observer's FOV. This demonstrates the
importance of measuring ambient light levels and surface reflection coefficients in order to maximise adaptation and
observer's perception of low contrast detail and minimise eye strain.