Interpretation of Positron Emission Mammography and MRI by Experienced Breast Imaging Radiologists: Performance and Observer Reproducibility

In preparation for a multicenter trial of positron emission mammography (PEM) and MRI in women with newly diagnosed cancer, the two purposes of this study were to validate training of breast imagers in standardized interpretation of PEM and to validate performance of the same specialists interpreting MRI. A 2-hour didactic module was developed to train Mammography Quality Standards Act-qualified radiologist observers to interpret PEM images, consisting of a sample feature analysis lexicon analogous to BI-RADS and 12 sample cases. Observers were then asked to review separate interpretive skills tasks for PEM (49 breasts, 20 [41%] of which were malignant) and MRI (32 breasts, 11 [34%] of which were malignant), describe findings, and give assessments analogous to BI-RADS (category 1, 2, 3, 4A, 4B, 4C, or 5). Demographic experience variables were collected for 36 observers from 15 sites. Performance against histopathologic truth was determined, and interobserver agreement for classifying features and final assessments was evaluated using kappa statistics. Across 36 observers, mean sensitivity, specificity, and area under the curve (AUC) for PEM were 96% (range, 75-100%), 84% (range, 66-97%), and 0.95 (range, 0.82-1.0), respectively. Mean sensitivity, specificity, and AUC for the MRI task were 82% (range, 45-100%), 67% (range, 38-91%), and 0.80 (range, 0.48-0.96), respectively. Interobserver agreement for PEM findings ranged from moderate to substantial, with kappa values of 0.57 for lesion type and 0.63 for final assessments. With minimal training, experienced breast imagers showed high performance in interpreting PEM images. Performance in MRI interpretation by the same observers validated expected clinical practice.