Global and segmented search for lung nodules of different edge gradients.

Chest films were inspected by staff and resident radiologists for lung nodules under two viewing conditions: segmented search, in which films were divided into six sections and viewed piecemeal, and global search, in which the complete film was presented and viewed in its entirety. Nodules varied in edge gradient from sharp to fuzzy. Nodules with sharper edges were identified faster, more frequently, and with higher confidence than nodules with less sharp edges. Segmented search did not increase the probability of nodule detection; rather, it led to an increase in the number of false-positives, resulting in lower overall performance when compared with global search. The results are interpreted according to a visual search model which calls for the use of comparative scanning strategies to differentiate nodule-containing areas from nodule-free areas on chest films.