Detection of Small Hypervascular Hepatocellular Carcinomas in Cirrhotic Patients: Comparison of Superparamagnetic Iron Oxide-Enhanced MR Imaging with Dual-Phase Spiral CT

OBJECTIVE To compare the performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) maging at 1.5T and dual-phase spiral computed tomography (CT) for the depiction of small hypervascular hepatocellular carcinomas (HCCs). MATERIALS AND METHODS Forty-three patients with 70 small nodular HCCs (5-20 mm; mean, 13.7 mm) were examined. Diagnosis was based on the results of surgical biopsy in 22 patients and by the combined assessment of MR imaging, lipiodol CT, alpha feto-protein levels, and angiographic findings in 21. MR imaging consisted of respiratory-triggered turbo spin-echo T2-weighted imaging, T1-weighted fast low-angle shot, and T2* -weighted fast imaging with steady-state precession imaging before and after SPIO enhancement. CT imaging was performed with 5-mm collimation and 1:1.4 pitch, and began 30 and 65 secs after the injection of 150 mL of contrast medium at a rate of 3 mL/sec. Two blinded observers reviewed all images independently on a segment-by-segment basis. Diagnostic accuracy was evaluated using receiver operating characteristics(ROC) analysis. RESULTS The mean areas (Az) under the ROC curves were 0.85 for SPIOenhanced MR imaging and 0.79 for dual-phase spiral CT (p <.05). The mean sensitivity of SPIO-enhanced MR imaging was significantly higher than that of CT (p <.05), i.e. 70.6% for MR imaging and 58.1% for CT. MR imaging had higher false-positive rates than dual-phase spiral CT, but the difference was not statistically significant (3.7% vs 3.3%) (p >.05). CONCLUSION SPIO-enhanced MR imaging is more sensitive than dual-phase spiral CT for the depiction of small hypervascular hepatocellular carcinomas.