Utility of Diffusion-Weighted MRI to Detect Changes in Liver Diffusion in Benign and Malignant Distal Bile Duct Obstruction: The Influence of Choice of b-Values.

PURPOSE: The study sought to evaluate the potential of diffusion-weighted magnetic resonance imaging to detect changes in liver diffusion in benign and malignant distal bile duct obstruction and to investigate the effect of the choice of b-values on apparent diffusion coefficient (ADC). METHODS: Diffusion-weighted imaging was acquired with b-values of 200, 600, 800, and 1000 s/mm2. ADC values were obtained in 4 segments of the liver. The mean ADC values of 16 patients with malignant distal bile duct obstruction, 14 patients with benign distal bile duct obstruction, and a control group of 16 healthy patients were compared. RESULTS: Mean ADC values for 4 liver segments were lower in the malignant obstruction group than in the benign obstruction and control groups using b = 200 s/mm2 (P < .05). Mean ADC values of the left lobe medial and lateral segments were lower in the malignant obstruction group than in the benign obstructive and control groups using b = 600 s/mm2 (P < .05). Mean ADC values of the right lobe posterior segment were lower in the malignant and benign obstruction groups than in the control group using b = 1000 s/mm2 (P < .05). Using b = 800 s/mm2, ADC values of all 4 liver segments in each group were not significantly different (P > .05). There were no correlations between the ADC values of liver segments and liver function tests. CONCLUSION: Measurement of ADC shows good potential for detecting changes in liver diffusion in patients with distal bile duct obstruction. Calculated ADC values were affected by the choice of b-values.