Differential diagnosis of hepatic nodules using delayed parenchymal phase imaging of levovist contrast ultrasound: comparative study with SPIO-MRI.

T2-weighted fast spin echo images and T2*-weighted gradient-echo images of superparamagnetic iron oxide magnetic resonance imaging (SPIO-MRI) have been reported to reflect the number and function of macrophages in reticuloendothelial organs and be useful to differentiate malignant tumors from benign nodules of liver. We tried to prove that contrast-enhanced ultrasound can diagnose hepatocellular carcinoma (HCC) by comparing the findings of SPIO-MRI and the findings of the liver parenchyma on the delayed parenchymal phase of ultrasound imaging using the intravenous contrast agent Levovist, not through the evaluation of vascular imaging. Forty-six patients (52 nodules) with histopathological diagnosis of hepatic tumors were studied. They consisted of 11 non-malignant nodules (six regenerative nodules and five dysplastic nodules) and 41 HCC. All the patients were examined by Levovist contrast-enhanced ultrasonography and SPIO-MRI. The delayed liver parenchymal images of contrast-enhanced ultrasound using the intravenous contrast agent Levovist were similar to those observed on SPIO-MRI. The similarity of both findings suggests that delayed phase imaging by Levovist is closely related to the number and function of Kupffer cells in liver tumors. The diagnostic accuracy of contrast-enhanced ultrasound for HCC was high (90.4%) demonstrating that it is as reliable as SPIO-MRI.