Quantitative analysis of diffusion-weighted magnetic resonance imaging in malignant breast lesions using different b value combinations

OBJECTIVES: To explore how apparent diffusion coefficients (ADCs) in malignant breast lesions are affected by selection of b values in the monoexponential model and to compare ADCs with diffusion coefficients (Ds) obtained from the biexponential model. METHODS: Twenty-four women (mean age 51.3 years) with locally advanced breast cancer were included in this study. Pre-treatment diffusion-weighted magnetic resonance imaging was performed using a 1.5-T system with b values of 0, 50, 100, 250 and 800 s/mm(2). Thirteen different b value combinations were used to derive individual monoexponential ADC maps. All b values were used in the biexponential model. RESULTS: Median ADC (including all b values) and D were 1.04 × 10(-3) mm(2)/s (range 0.82–1.61 × 10(-3) mm(2)/s) and 0.84 × 10(-3) mm(2)/s (range 0.17–1.56 × 10(-3) mm(2)/s), respectively. There was a strong positive correlation between ADCs and Ds. For clinically relevant b value combinations, maximum deviation between ADCs including and excluding low b values (<100 s/mm(2)) was 11.8 %. CONCLUSION: Selection of b values strongly affects ADCs of malignant breast lesions. However, by excluding low b values, ADCs approach biexponential Ds, demonstrating that microperfusion influences the diffusion signal. Thus, care should be taken when ADC calculation includes low b values. KEY POINTS: • Diffusion-weighted sequences are increasingly used in breast magnetic resonance imaging • Diffusion-weighting (b) values strongly influence apparent diffusion coefficients of malignant lesions • Exclusion of low b values reduces the apparent diffusion coefficient • Flow-insensitive monoexponential apparent diffusion coefficients approach biexponential diffusion coefficients