Feasibility of Different b-Values of MRI Diffusion in Quantitative Assessment of Liver Fibrosis

Abstract

Purpose: We aimed to assess the accuracy of hepatic ADC and the best b-value for diffusion-weighted imaging (DWI) for quantification of liver fibrosis, aiming to improve diagnostic accuracy, in order to achieve a reliable non invasive marker of hepatic fibrosis. Materials & Methods: One hundred patients with history of chronic hepatitis C virus and twenty five healthy adult volunteers control group were investigated by diffusion MRI in the axial plane, during a single end expiratory breath-hold at different b-values of (200, 500, 700 and 1000 s/mm2) on the same day before liver biopsy. ADC maps were generated and the mean hepatic ADC was calculated as the arithmetic mean of the four hepatic ADC values calculated at each b-value. Liver ADCs were correlated with fibrosis scores using the Spearman’s rank correlation coefficient, while Receiver Operating Characteristic (ROC) curve analysis was used to determine the area under the ROC curve (AUC), and the threshold ADC was used to maximize the average of sensitivity and specificity. Results: The patient group were stratified pathologically according to modified Ishak classification as stage 1 to stage 6 (n=14, 40, 28, 5, 28, 4 and 9 patients respectively). We achieved negative correlation between the ADC values and the degree of liver fibrosis at b-values 200 and 1000 s/mm2, respectively, with P=0.000. The ROC curve analysis at b-value =1000 s∕mm 2 , revealed significant difference in ADC values between patients with early fibrosis (F≤4) and those with cirrhotic liver (F≥5) (p=0.000), where the best cut off ADC value to distinguish between these groups was 1.12 x 10 -3 mm 2 /s, with 80.5% sensitivity and 77% specificity. Conclusion: Liver ADC showed a significant difference in the ADC values of nonfibrotic and cirrhotic patients, with high sensitivity and specificity at b-value 1000 s/mm 2 with cut off value 1.12 x 10 -3 mm 2 /s.