Improving outcomes of screening breast MRI with practice evolution: initial clinical experience with 3T compared to 1.5T.

PURPOSE

To determine if changing from 1.5T to 3T breast magnetic resonance imaging (MRI) is associated with a change in BI-RADS categories, positive predictive value of biopsy recommendation, or cancer detection rates in high-risk screening breast MRI.

MATERIALS AND METHODS

Institutional Review Board (IRB) approval was obtained for this Health Insurance Portability and Accountability Act (HIPAA)-compatible retrospective review. Prior to October 2010, breast MRI was performed at 1.5T and after October 2010 breast MRI was performed at 3T. Reports of 495 consecutive screening 3T breast MRI exams from October 2010 through October 2011 were reviewed. Comparison was made to previously collected data on 650 screening breast MRI exams at 1.5T. Data were analyzed for statistical significance using the two-sample test of proportions.

RESULTS

There were 495 screening breast MRI exams. There were 419 (84.6%) BI-RADS 1/2 results, 35 (7.1%) BI-RADS 3 results, and 41 (8.3%) BI-RADS 4/5 results. BI-RADS 4/5 results increased at 3T (P=0.04). The positive predictive value for BI-RADS 4/5 was 29.3% (12/41) at 3T, compared with 17.6% at 1.5T (P<0.001). Cancer detection rate was 2.6% at 3T, compared with 0.9% at 1.5T (P=0.02).

CONCLUSION

Transition to 3T breast MRI in a screening population resulted in increased BI-RADS 4/5 interpretations, positive predictive value of biopsy recommendations, and cancer detection rate.