Relating the perceived useful field of view to visual search in 2D Images and 3D volumetric images

3D volumetric images are prevalent in industries ranging from radiology and oncology to airport luggage screenings. With 3D medical images, however, radiologists are visually overburdened by the vast amount of image data requiring inspection. Radiologists and trained (nonradiologist) observers often underexplore 3D images with eye movements-producing misses of small targets undetectable in the visual periphery. We investigate why observers underexplore 3D images by quantifying their perceived exploration of the search area and relating it to the extent of their search on trials where they report "target absent." Six trained observers participated in two eye-tracking experiments to evaluate whether the area covered by the Useful Field of View (UFOV) influences the underexploration of the 3D images. Experiment 1 estimated empirical and perceived target-specific UFOVs per observer. We tested the observer's detectability of a small and large target embedded in 1/f noise as a function of retinal eccentricity (empirical UFOV). Observers also estimated how well they could see the two targets in their visual periphery (perceived UFOV). Experiment 2 had observers participate in a 2D and a 3D search for the two targets. The area covered with the perceived but not empirical UFOVs was similar across targets in the 2D and 3D searches. Moreover, while performing the 3D search, observers covered the 2D projection plane (i.e., collapsing all slices that comprise the 3D volumetric image into one image plane) with their perceived UFOVs to the same extent as in the 2D search task, leaving much of the 3D volume unexplored.