RESUMO
OBJECTIVE: To investigate the performance of different b values and regions of interest (ROI) for diagnosing liver fibrosis in patients with chronic viral hepatitis by using diffusion-weighted (DW) magnetic resonance imaging (MRI). METHODS: Eleven healthy participants and 33 patients with viral hepatitis B or C were enrolled. The stage of liver fibrosis and the grade of necroinflammation were determined by using a histologic activity index. Single-shot spin-echo echo-planar DW-MRI was performed in all participants at b values of 0-500, 0-700, and 0-1000 s/mm(2) by using 2 circular small and large ROIs of 100 and 200 mm(2). To evaluate the performance of different b values for determining cirrhosis, the receiver-operating characteristic curves were depicted, and the areas under the curves were compared. RESULTS: The average values of apparent diffusion coefficients significantly decreased with increasing stage or grade categories at all the 3 b values and for both small and large ROIs. The performance at b = 500 s/mm(2) was significantly better than b = 1000 s/mm(2) for determining cirrhosis or bridging fibrosis. The cut point of 153.4 for apparent diffusion coefficient (×10(-5) mm(2)/s) at b = 500 s/mm(2) could determine cirrhosis or bridging fibrosis with a sensitivity of 96% and specificity of 82%. No difference was found between the average apparent diffusion coefficient values of large or small ROIs. Also, there was no difference in performance of large or small ROIs in the diagnosis of liver fibrosis. CONCLUSIONS: This study provided beneficial data for clinical utilisation of DW-MRI in diagnosing liver fibrosis: b = 500 s/mm(2) is better in performance than b = 1000 s/mm(2), and a small ROI of 100 mm(2) is sufficient for determining cirrhosis or bridging fibrosis.
