In Review - News from the 2004 Meeting of the RSNA

Contrast ultrasound zeroes in on focal liver lesions

CE sonography plays increasing role in HCC screening abroad, but U.S rads prefer MR or CT

By: H.A. Abella

While Asian, Canadian, and European researchers seem to agree that ultrasound is the modality of choice for initial triage of liver tumors, U.S. radiologists stand apart. This trend was apparent at the RSNA meeting, where a group of papers from overseas researchers offered compelling evidence that contrast-enhanced ultrasound can not only reliably characterize focal liver lesions but can also obviate more invasive and costly imaging.

"There were more than 100 abstracts submitted on contrast agent evaluations for the liver this year, and virtually none of them were from the U.S.," said Dr. Stephanie R. Wilson, a radiologist at the University of Toronto, who chaired one of the gastrointestinal sessions.

U.S. radiologists rely primarily on CT and MR imaging. Their entrenchment in these technologies, plus the FDA's lack of receptiveness to alternative approaches, undermines the cost-effectiveness of healthcare in this country and exposes patients to unnecessary risk, Wilson said.

In one study, Canadian researchers used contrast-enhanced ultrasound to evaluate 80 patients with 106 hepatic nodules with a high likelihood of becoming malignant. They found that contrast ultrasound could characterize lesions early and avoid further scanning with CT or MR.

Contrast ultrasound confirmed 46 lesions as hepatocellular carcinoma, 31 as dysplastic/regenerative nodules, 16 as hemangiomas, eight as pseudomasses, and five as indeterminate nodules.

In a similar study, Italian researchers enrolled 191 consecutive patients with chronic diffuse liver disease due to chronic hepatitis B or C or cirrhosis. Using microbubble contrast ultrasound, they accurately differentiated HCCs from other focal liver lesions.

As in the previous study, the investigators used the lesions' enhancement patterns at different phases to calculate positive predictive values.

The investigators obtained the highest positive predictive value for HCC by combining diffuse heterogeneous enhancement at arterial phase with hypoechoic appearance at late phase, with a PPV of 94% and 92% overall accuracy in HCC characterization.