Hepatic tumors: US contrast enhancement with CO2 microbubbles.

Enhancement of hepatic tumors on sonograms by injection of carbon dioxide microbubbles into the hepatic artery as a contrast material (enhanced ultrasonography) was performed in 43 patients with various histologically confirmed hepatic tumors. Enhanced sonograms were classified into five patterns according to the relative changes of the echo levels between the tumor and the nontumorous parenchyma of the liver as a result of enhancement: hyperechoic change, isoechoic change, hypoechoic change with hyperechoic rim (rim sign), marginal spotty hyperechoic change, and internal spotty hyperechoic change. Eighty-eight percent of hepatocellular carcinomas showed hyperechoic change, 70% of metastatic tumors exhibited hypoechoic change with the rim sign. The marginal spotty hyperechoic change and the internal spotty hyperechoic change were specific for cavernous hemangioma and fibrous granuloma, respectively. This method of enhancement is useful in assessing the nature of liver tumors and in the detection of small nodules in the liver.