Digital Breast Tomosynthesis Slab Thickness: Impact on Reader Performance and Interpretation Time

Background Digital breast tomosynthesis (DBT) helps reduce recall rates and improve cancer detection compared with two-dimensional (2D) mammography but has a longer interpretation time. Purpose To evaluate the effect of DBT slab thickness and overlap on reader performance and interpretation time in the absence of 1-mm slices. Materials and Methods In this retrospective HIPAA-compliant multireader study of DBT examinations performed between August 2013 and July 2017, four fellowship-trained breast imaging radiologists blinded to final histologic findings interpreted DBT examinations by using a standard protocol (10-mm slabs with 5-mm overlap, 1-mm slices, synthetic 2D mammogram) and an experimental protocol (6-mm slabs with 3-mm overlap, synthetic 2D mammogram) with a crossover design. Among the 122 DBT examinations, 74 mammographic findings had final histologic findings, including 31 masses (26 malignant), 20 groups of calcifications (12 malignant), 18 architectural distortions (15 malignant), and five asymmetries (two malignant). Durations of reader interpretations were recorded. Comparisons were made by using receiver operating characteristic curves for diagnostic performance and paired t tests for continuous variables. Results Among 122 women, mean age was 58.6 years ± 10.1 (standard deviation). For detection of malignancy, areas under the receiver operating characteristic curves were similar between protocols (range, 0.83-0.94 vs 0.84-0.92; P ≥ .63). Mean DBT interpretation time was shorter with the experimental protocol for three of four readers (reader 1, 5.6 minutes ± 1.7 vs 4.7 minutes ± 1.4 [P < .001]; reader 2, 2.8 minutes ± 1.1 vs 2.3 minutes ± 1.0 [P = .001]; reader 3, 3.6 minutes ± 1.4 vs 3.3 minutes ± 1.3 [P = .17]; reader 4, 4.3 minutes ± 1.0 vs 3.8 minutes ± 1.1 [P ≤ .001]), with 72% reduction in both mean number of images and mean file size (P < .001 for both). Conclusion A digital breast tomosynthesis reconstruction protocol that uses 6-mm slabs with 3-mm overlap, without 1-mm slices, had similar diagnostic performance compared with the standard protocol and led to a reduced interpretation time for three of four readers. © RSNA, 2020 See also the editorial by Chang in this issue.