Impact of diffusion-weighted MR imaging on the characterization of small hepatocellular carcinoma in the cirrhotic liver

Abstract Purpose The purpose of this study was to determine whether or not adding diffusion-weighted magnetic resonance imaging (DWI) to conventional magnetic resonance (MR) imaging sequences improves the characterization of small hepatocellular carcinoma (HCC) (≤2 cm) in the setting of cirrhotic liver compared to conventional sequences alone. Materials and Methods A total of 62 cirrhotic liver patients with 82 nodules smaller than 2 cm in diameter were enrolled, and all lesions were pathologically confirmed. For the first reading session, which included precontrast T1- and T2-weighted images and T1 dynamic contrast-enhanced images, preindicated lesions by a study coordinator were characterized by two radiologists. They determined the confidence levels in consensus for the presence of small HCC into four grades. In another session, respiratory-triggered diffusion-weighted MR images ( b factor=50, 400 and 800 s/mm2 ) were added to the previously reviewed images, and the same two radiologists again determined the confidence levels. The diagnostic performance of the combined DWI–conventional sequences set and the conventional sequences alone set was evaluated using receiver operating characteristic curves. Sensitivity and specificity values for characterizing small HCCs were also calculated. Results The area under the receiver operating characteristic curve for the second interpretation session (0.86) was significantly higher ( P =.038) than that of the first session (0.76). The sensitivity was significantly increased from 75.7% to 87.8% by adding DWI to the conventional sequences ( P =.015). No significant differences were observed for specificity values. Conclusion Adding DWI to conventional imaging modalities improves the diagnosis of small HCCs in the cirrhotic liver in terms of diagnostic performance and sensitivity by increasing reader confidence.