Diffusion magnetic resonance imaging of breast lesions: Initial experience at Alexandria University

Objective: The purpose of our study was to investigate whether adding diffusion weighted imaging (DWI) to dynamic contrast-enhanced MRI (DCE-MRI) could improve specificity and the positive predictive value (PPV) of breast MRI in differentiating benign and malignant focal breast mass lesions. Materials and methods: The prospective study included 71 females with 103 focal breast lesions on DCE-MRI who underwent subsequent biopsy. DWI was acquired during diagnostic breast MRI using b = 0, 400 and 800 s/mm2. Apparent diffusion coefficient (ADC) values were compared for benign and malignant lesions. Sensitivity and PPV were calculated for DCE-MRI alone (based on biopsy recommendations) and DCE-MRI plus DWI (adding an ADC threshold) for the same set of lesions. Results: On pathological basis, 57 out of 103 focal lesions were benign and the remaining revealed, 45 were malignant and one borderline. Malignant lesions exhibited lower mean ADC (1.3 × 10−3 mm2/s). Applying an ADC threshold of 1.3 × 10−3 mm2/s sensitivity increased (on conventional DCE-MRI basis) from 86.95% up to 93.47% and the specificity from 91.22% to 96.49% in detection of malignancy with PPV of 95.55% in comparison to 86.95% for enhancement kinetics alone, which would have avoided biopsy for 10.5% (6/57) of benign lesions without missing any cancers. Conclusion: DWI shows potential for improving the PPV of breast MRI for detection of malignant breast lesions. Recommendation: Furthermore, larger studies should be made to use it as a monitor for tumor response to chemotherapy. KEYWORDS: Apparent diffusion coefficient, Breast, Diffusion-weighted MRI, Magnetic resonance mammography, MRM, Positive predictive value