Diffusion-weighted MRI and optimal b-value for characterization of liver lesions

Background: Diffusion-weighted imaging (DWI) is commonly used to distinguish between benign and malignant liver lesions. However, different b-values are recommended. Purpose: To determine the most suitable b-value in DWI for differentiation of benign and malignant liver lesions. Material and Methods: A total of 124 lesions in 89 consecutive patients (43 men, 46 women; age, mean +/- standard deviation, 58 +/- 14 years) with a pathological or radiological diagnosis of malignant or benign focal liver lesions after magnetic resonance imaging (MRI) were included in this study. Routine abdominal MRI and DWI were performed using seven b-values (0, 50, 200, 400, 600, 800, 1000 s/mm(2)). Lesions were analyzed for benignity/malignity using apparent diffusion coefficient (ADC) values with 10 b-value combinations and by measuring the lesion/normal parenchyma ADC ratio. Results: Mean ADC values were significantly different between malignant and benign lesions for all b-value combinations (P = 0.000). The best b-value combination was 0 and 800 (Az = 0.935). Using lower b-values such as 0 and 50 together with higher b-values >= 600 s/mm(2) was beneficial (Az = 0.928 and 0.927). Mean ADC values were approximately 13% (1-15%) higher in total when b = 0 and b = 50 s/mm(2) were included in multiple b-value combinations. Conclusion: In DWI, we recommend the use of b-values of 0 and 800 s/mm(2) as two b-values, or b = 0, 50, 600, 800, and 1000 s/mm(2) as multiple b-values for distinguishing between benign and malignant liver lesions. Mean ADC value is 13% higher in total by additional use of b = 0 and b = 50 s/mm(2) in multiple b-value combinations.