Suspicious minds: effect of using a lesion likelihood score on reader behaviour with interactive mammographic CAD

Abstract

Computer-Aided Detection (CAD) systems are used to help readers in interpreting screening mammograms. Traditional use of CAD in mammography involves an expert reader searching the image initially unaided, and then once again with the aid of CAD prompts that automatically indicate suspicious regions. An alternative approach is interactive CAD, where prompts are only displayed when readers query a suspicious region for which a prompt is available. These prompts are typically displayed with a given confidence of malignancy for that region. Two non-expert observer studies of interactive CAD were conducted to investigate its effect on the visual search of synthetic images containing microcalcification clusters. Experiment 1 (n=44) used no-CAD and interactive CAD conditions, whereas Experiment 2 (n=43) used interactive CAD in both conditions but in one there was an additional ‘image score’ denoting the likelihood that an image contained a cluster. In both experiments, the addition of interactive CAD (Experiment 1) and an image score (Experiment 2) did not change sensitivity or specificity compared to no-CAD and interactive CAD-alone, respectively. In Experiment 1, the higher the confidence value for a given prompt, the more likely a participant was to act on it. This effect was stronger for true prompts than false prompts. In Experiment 2, participants spent longer viewing images with higher image scores. When no prompt was available, they were more likely to make false positive errors on those images. However, decisions made on available prompts were influenced primarily by confidence values of the prompts rather than overall image score.