Purpose: To prospectively examine operator dependence of lesion detection, description, and interpretation when experienced breast radiologists perform whole-breast ultrasonography (US).

Materials and methods: Institutional review board approval was obtained for the HIPAA-compliant study. Ten women (aged 19-53 years; mean, 37.4 years; 20 breasts) with numerous known breast lesions consented to participate. Eleven breast radiologists, who passed experience and qualification requirements for a screening breast US trial and consented to participate, scanned both breasts in all participants and documented images of each detected lesion and its size, location, features, palpability, and Breast Imaging Reporting and Data System final assessment. Intraclass correlation coefficients (ICCs) were used to measure agreement on lesion size and location, and kappa statistics were calculated for agreement on features and final assessments compared with consensus.

Results: Eighty-eight unique lesions were identified by at least two investigators (five to 13 lesions per participant). Mean diameter was 6.7 mm (standard error, 0.4; range, 2-22 mm), and eight lesions (9%) were palpable. Of 968 potential detections (88 lesions, 11 investigators), 536 (55%) detections were made. Individual investigators detected between 43 (49%) and 58 (66%) lesions. Larger lesions were more consistently detected: Detection rates were six of 33 lesions (18%) at 3 mm or smaller; 164 of 374 (43.9%) at 3.1-5 mm; 145 of 275 (52.7%) at 5.1-7 mm; 119 of 176 (67.6%) at 7.1-9 mm; 38 of 44 (86%) at 9.1-11 mm; and 64 of 66 (97%) lesions larger than 11 mm (P < .001). ICCs for clockface, distance from nipple, and individual lesion diameter all exceeded 0.7, indicating high reliability. For shape, margins, and final assessments of solid lesions, kappa values were 0.62, 0.67 (substantial agreement), and 0.52 (moderate agreement), respectively. Of 110 detections of consensus cysts 8 mm and smaller, 15 (14%) detections were considered to be of solid lesions by at least one reader.

Conclusion: Larger lesions (>11 mm) are most consistently detected, with fewer than half of lesions 5 mm or smaller in mean diameter identified; substantial agreement was found for description of lesion size, location, and key features, and moderate agreement was found for lesion management.