<title>Effect of Toto circle and mammographic background size on detection performance</title>

Abstract

Kundel et al. Suggested the use of circle cues to assist human observers during signal-known-exactly (SKE) detection experiments. The circles were bipolar (with concentric black and white rings) and centered on potential locations of simulated masses added to mammographic backgrounds. They used a large circle cue (diameter 6.4 cm) and a background size of 7.7 cm (referred to the initial mammogram). They found significant detection performance improvement compared to the no cue conditions. In our previous experiments, we use mammographic background sizes of 6.1 cm and smaller circles with sizes dependent on lesion size. Our circle sizes were selected to subjectively optimize utility but choices may not have been the best. Also, detectability may also depend on background size. In this work, we present human observer results for detecting a realist mass added to mammographic backgrounds using 30 conditions (all combinations of the mass scaled to 3 sizes, 2 background sizes and 5 circle sizes). Performance did not depend on background size. For the smallest mass size (1 mm, 8 pixels), detectability decreased as circle size increased. There may be an optimum near a circle/mass size ratio of 4. The optimum size ratio for the 4 mm mass was 3. For the 16 mm mass, detectability decreased as steadily as circle size increased. The smallest size ratio used was 1.2.