Intravoxel Incoherent Motion Diffusion-Weighted Imaging for Characterizing Focal Hepatic Lesions: Correlation With Lesion Enhancement

Purpose To evaluate the value of intravoxel incoherent motion (IVIM) parameters for characterizing focal hepatic lesions, and to assess the correlation between IVIM parameters and arterial nodule enhancement. Materials and Methods We retrospectively evaluated 161 lesions (91 hepatocellular carcinomas [HCCs], 27 intrahepatic cholangiocarcinomas [IHCCs], 20 hemangiomas, 9 combined hepatocellular-cholangiocarcinomas, 9 metastases, and 5 other tumors) in 161 patients (105 men and 56 women; mean age, 56.4 years). Diffusion-weighted imaging was performed using nine b-values (0-900 s/mm(2)) at 1.5T. Apparent diffusion coefficient (ADC), molecular diffusion coefficient (D-slow), perfusion fraction (f), and perfusion-related diffusion coefficient (D-fast) were compared among the hepatic lesions using analysis of variance (ANOVA). Receiver-operating-characteristic analysis was performed to assess diagnostic performance. The enhancement fraction (EF) and the relative enhancement (RE) of the hepatic lesions on arterial phase gadoxetic acid-enhanced images were correlated with the IVIM parameters using Spearman's test. Results For the differentiation of hemangiomas from malignant tumors, D-slow showed the largest area under the curve (0.933) among all parameters. Although ADC did not show any difference among malignant lesions (P > 0.28), HCCs showed a significantly lower D-slow than IHCC (P < 0.001) and a higher f than did IHCC (P < 0.001) and metastasis (P = 0.027); f had a significant positive correlation with EF (r = 0.420, P < 0.001) and RE (r = 0.264, P = 0.001). ConclusionI VIM parameters are more helpful in characterizing malignant hepatic lesions than ADC; f may reflect the extent and degree of hepatic nodule enhancement in the arterial phase, and may allow for differentiation of HCC from IHCC and metastasis.