Stratification of mammographic computerized analysis by BI-RADS categories

The Breast Imaging Reporting and Data System (BI-RADS) was implemented to standardize characterization of mammographic findings. The purpose of the present study was to evaluate in which BI-RADS categories the changes recommended by computerized mammographic analysis are most beneficial. Archival cases including, 170 masses (101 malignant, 69 benign) and 63 clusters of microcalcifications (MCs; 36 malignant, 27 benign), were evaluated retrospectively, using the BI-RADS categories, by several radiologists, blinded to the pathology results. A computerized system then automatically extracted from the digitized mammogram features characterizing mammographic lesions, which were used to classify the lesions. The results of the computerized classification scheme were compared, by receiver operating characteristics (ROC) analysis, to the conventional interpretation. In the "low probability of malignancy group" (excluding BI-RADS categories 4 and 5), computerized analysis improved the A(z )of the ROC curve significantly, from 0.57 to 0.89. In the "high probability of malignancy group" (mostly category 5) the computerized analysis yielded an ROC curve with an A(z )of 0.99. In the "intermediate probability of malignancy group" computerized analysis improved the A(z )significantly, from 0.66 for to 0.83. Pair-wise analysis showed that in the latter group the modifications resulting from computerized analysis were correct in 83% of cases. Computerized analysis has the ability to improve the performance of the radiologists exactly in the BI-RADS categories with the greatest difficulties in arriving at a correct diagnosis. It increased the performance significantly in the problematic group of "intermediate probability of malignancy" and pinpointed all the cases with missed cancers in the "low probability" group.