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Visualisation of anatomical or pathological image data is highly dependent on the eye's ability to discriminate between
image brightnesses and this is best achieved when these data are presented to the viewer at luminance levels to which the
eye is adapted. Current ambient light recommendations are often linked to overall monitor luminance but this relies on
specific regions of interest matching overall monitor brightness.
The current work investigates the luminances of specific regions of interest within three image-types: postero-anterior
(PA) chest; PA wrist; computerised tomography (CT) of the head. Luminance levels were measured within the hilar
region and peripheral lung distal radius and supra-ventricular grey matter. For each image type average monitor
luminances were calculated with a calibrated photometer at ambient light levels of 0, 100 and 400 lux. Thirty samples of
each image-type were employed, resulting in a total of over 6,000 measurements.
Results demonstrate that average monitor luminances varied from clinically-significant values by up to a factor of 4, 2
and 6 for chest, wrist and CT head images respectively. Values for the thoracic hilum and wrist were higher and for the
peripheral lung and CT brain lower than overall monitor levels. The ambient light level had no impact on the results.
The results demonstrate that clinically important radiological information for common radiological examinations is not
being presented to the viewer in a way that facilitates optimised visual adaptation and subsequent interpretation. The
importance of image-processing algorithms focussing on clinically-significant anatomical regions instead of radiographic
projections is highlighted.
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