Contrast-Enhanced Magnetic Resonance Mammography

Abstract

Rationale and Objectives. We refined and evaluated a spin-echo-based dynamic MR mammography technique for detection and characterization of benign and malignant breast masses. Methods. Analysis was performed on 75 magnetic resonance (MR) mammographies done at 0.5-T on 67 consecutive patients. Histological confirmation of malignancy and MR enhancement data were available on 33 cancers; 29 were infiltrating ductal carcinomas. Precontrast short inversion time (TI) inversion recovery images (TR 2000, TE 30, TI 110) were obtained as well as serial dynamic pre- and postcontrast T1-weighted spin-echo images (TR 600, TE 12) after bolus injection of 0.1 mmol/kg gadolinium chelate. An image subtraction technique was used, and tissue enhancement (expressed as a percentage of baseline signal intensity) was calculated for immediate (0 min) and delayed (8 min) studies. Lesion enhancement was compared to normal parenchyma, fat, muscle, and cysts. Coronal and sagittal reformatted images were also produced. Three cancers were studied during chemotherapy. Results. The mean immediate and delayed tumor enhancement values were 81 ± 22% and 84 ± 23%, respectively. Other tissue values were (immediate, delayed): normal breast, 7% and 19%; fat, 4% and 4%; muscle, 11% and 12%; cysts, 0% and 0%. Fibroadenomas may enhance as quickly and intensely as tumors, but are smooth and usually septated. Image subtraction substantially increased lesion contrast, although motion artifact and misregistration can compromise image quality and quantitation. Conclusion. Breast cancers enhance 10 times or more than normal breast parenchyma; this, together with the image subtraction method, results in high lesion conspicuity. Both quantitative enhancement profiles and morphological criteria are necessary to differentiate benign from malignant lesions. Although the technique, interpretive criteria, and indications are still evolving, MR mammography may play an important role in the future detection and staging of breast cancer.