Diagnostic performance of gadoxetic acid (Primovist)-enhanced MR imaging versus CT during hepatic arteriography and portography for small hypervascular hepatocellular carcinoma

To compare the diagnostic performance of gadoxetic acid-enhanced magnetic resonance imaging (MRI) with that of computed tomography (CT) during hepatic arteriography and arterial portography (CT HA/AP) for detecting hepatocellular carcinoma (HCC) from small hypervascular nodules. This retrospective study included 38 patients with 131 hypervascular nodules (≤2 cm) who had underwent MRI and CT HA/AP within a 2-week interval. Two observers analyzed MRI while other 2 observers analyzed CT HA/AP. Thereafter, MRI observers reviewed the CT HA/AP and magnetic resonance (MR) images again using both modalities. HCC was diagnosed by pathologic or imaging studies according to American Association for the Study of Liver Diseases (AASLD) criteria. Alternative free-response receiver operating characteristic (ROC) analysis was performed on a lesion-by-lesion basis. Diagnostic accuracy (area under the ROC curve [A(z)]), sensitivity, specificity, and positive and negative predictive values were calculated. The pooled A(z) was significantly higher for the combined modalities (0.946) than for MRI alone (0.9, P = 0.004), and for MRI than for CT HA/AP alone (0.827, P = 0.0154). Subgroup analysis for HCC ≤1 cm showed the sensitivity of the combined modalities (79.4%) was significantly higher than for MRI (52.9%) and CT HA/AP alone (50%) (both, P < 0.005). The specificity of the combined modalities was not different from MRI alone (98.8% vs. 97.3%, P = 0.5), but was significantly higher than for CT HA/AP alone (98.8% vs. 92.5%, P = 0.022). Hypervascular HCCs >1 to 2 cm can be diagnosed sufficiently by MRI. The combined modalities increased the diagnostic accuracy of HCCs ≤1 cm, compared with MRI or CT HA/AP alone.