Priming cases disturb visual search patterns in screening mammography

Rationale and Objectives: To investigate the effect of inserting obvious cancers into a screening set of mammograms on the visual search of radiologists. Previous research presents conflicting evidence as to the impact of priming in scenarios where prevalence is naturally low, such as in screening mammography. Materials and Methods: An observer performance and eye position analysis study was performed. Four expert breast radiologists were asked to interpret two sets of 40 screening mammograms. The Control Set contained 36 normal and 4 malignant cases (located at case # 9, 14, 25 and 37). The Primed Set contained the same 34 normal and 4 malignant cases (in the same location) plus 2 “primer” malignant cases replacing 2 normal cases (located at positions #20 and 34). Primer cases were defined as lower difficulty cases containing salient malignant features inserted before cases of greater difficulty. Results: Wilcoxon Signed Rank Test indicated no significant differences in sensitivity or specificity between the two sets (P > 0.05). The fixation count in the malignant cases (#25, 37) in the Primed Set after viewing the primer cases (#20, 34) decreased significantly (Z = -2.330, P = 0.020). False-Negatives errors were mostly due to sampling in the Primed Set (75%) in contrast to in the Control Set (25%). Conclusion: The overall performance of radiologists is not affected by the inclusion of obvious cancer cases. However, changes in visual search behavior, as measured by eye-position recording, suggests visual disturbance by the inclusion of priming cases in screening mammography.