Early detection and characterization of hepatocellular carcinoma: value of imaging multistep human hepatocarcinogenesis

The method for early detection of hepatocellular carcinoma (HCC) has been well established in Japan, by means of regularly screening patients at risk for developing HCC by imaging and serological markers of tumor. The principal screening protocol includes performing ultrasonography (US) every 3 months and testing for tumor markers every month in patients at high risk for HCC. There has been another important issue of accurate characterization of nodular lesions found in cirrhotic liver. This problem has been solved by the development of imaging modalities such as US angiography with intra-arterial injection of CO(2), computed tomography during hepatic arteriography and computed tomography during arterial portography. It is most important to differentiate the typical hemodynamic patterns of a low-grade dysplastic nodule having arterial hypovascularity with portal perfusion preserved from those of HCC characterized by arterial hypervascularity with decreased portal perfusion. At present, these findings are easily obtained by contrast-enhanced phase invasion harmonic imaging, which is a noninvasive US technology.