Detection of small low-contrast objects in mammography: Effect of viewbox masking and luminance

OBJECTIVE. Viewing conditions can affect an observer's performance in object detection, Our objective was to determine the effect of viewbox masking and luminance on the detection of small low-contrast objects revealed by mammography. MATERIALS AND METHODS. Mammographic contrast-detail images having various film densities were viewed on masked and unmasked viewboxes. Similar images with fixed film contrast and density were viewed when luminance ranged from 250 to 8000 nits (1 nit = 1 cd/m(2)), RESULTS. Detection of small low-contrast objects was significantly easier using a masked viewbox with high luminance than using a regular unmasked viewbox. When a regular viewbox (approximately 3000 nits) was used, masking had a more significant effect on films with high optical densities than on films with low optical densities. Brighter, masked viewboxes improved detection on films with higher optical densities. CONCLUSION. Better detection of small low-contrast objects results when mammographic images are masked and viewed on high-luminance viewboxes than when a regular unmasked viewbox is used.