Corona enhancement in ultrasonographical post-vascular phase images with microbubble contrast agent: a novel specific sign for hepatocellular carcinomas.

In 1.5 Harmonic Imaging ultrasonography (1.5 HI US), images are obtained in a band intermediate between the fundamental and 2nd harmonic components, resulting in stronger contrast enhancement than in conventional harmonic imaging. We attempted to assess the hemodynamics of hepatocellular carcinomas (HCC) with special attention to blood drainage using 1.5 HI US. Forty-two HCC nodules, metastatic liver tumors and hepatic hemangiomas were studied. In contrast studies, intermittent ultrasound transmission was performed for a period of up to 45 sec after the injection of contrast agent, which was regarded as the vascular phase. The time point of 5 min later was specified as the post-vascular phase, and images were obtained by single manual transmission for comparison of contrast enhancement with surrounding hepatic parenchyma. In addition, histological examination was performed. 1.5 HI US clearly demonstrated the strong tumor vessels in most HCCs. Corona enhancement, in which the areas surrounding the tumor are enhanced, was observed in 71.4% (30/42) of HCC nodules during the post-vascular phase. This sign was not observed in any other tumors. Histological findings revealed that CD34-positive-endothelial cells were prominent in the surrounding area of HCC. In conclusion, 1.5 HI US is an effective tool for evaluating hemodynamics in both early- and post-vascular phase. Corona enhancement may be due to the trapping of contrast agent in the endothelial cells in the surround of HCC nodules and be a novel specific sign for HCC.