Abstract
Radiologists must classify and interpret medical images on the basis of visual inspection. We are examining how an observer’s visual sensitivity and perception might change as they view and thus adapt to the characteristic properties of radiological scans. Measurements were focused on the effects of adaptation to images of normal mammograms, and were tested in observers who were not radiologists. These scans have steeper power spectra (slopes of ~-3) than natural images (~-2) and thus are physically blurry. To test for adaptation specific to this blur, we measured contrast sensitivity for Gabor patches after observers viewed a sequence of randomly sampled sections from mammograms. Sensitivity was selectively reduced at lower spatial frequencies (less than ~2 c/deg), consistent with an adaptation to the low-frequency bias in the images. However, similar sensitivity losses were also found when the images were sharpened to have more "natural" spectra, suggesting that the blur in the scans was not sufficient to substantially change threshold sensitivity relative to the observer’s natural operating state. In contrast, aftereffects specific to the image blur were found when observers instead judged the perceived blur within the images, by adjusting the spectral slope of a comparison image presented to an unadapted retinal location. Strong aftereffects in the appearance of the images were also found when observers judged the perceived texture of the images. For example, tissue density in mammograms is routinely classified and ranges from "dense" to "fatty." Adaptation to dense images caused an intermediate image to appear more fatty and vice versa. Our results suggest that observers can selectively adapt to the properties of radiological images, and that this selectivity could especially impact the perceived textural characteristics of the images.
Meeting abstract presented at VSS 2012