MR contrast agent improves liver imaging, allows cholangiography

Primovist improves MR detection of liver lesions and can change the surgical management of patients in a substantial number of cases, according to the results of two studies presented at the ECR Friday. The data were part of a symposium sponsored by Schering, the developer of the liver-specific agent.

Dr. Renate Hammerstingl, a radiologist at the Institute of Diagnostic and Interventional Radiology, University of Frankfurt/Main, concluded that patients benefit the most from the use of Primovist if they are evaluated with the agent as part of their diagnostic workup. CLICK HERE FOR VIDEO CLIP

Hammerstingl and colleagues found in a study of 131 patients use of the agent led to a change in surgical therapy in 14.5% of patients diagnosed with focal liver lesions. The study established the equivalence of Primovist-enhanced MR to spiral CT, the de facto benchmark in the diagnosis of liver lesions, and documented that contrast-enhanced MR reliably identified lesions 1 cm and less.

In a second study of 176 patients addressing characterization, the combination of precontrast and Primovist-enhanced MR correctly characterized a significantly higher proportion of lesions than CT. Overall, sensitivity, specificity, and accuracy for lesion classification improved with the MR regimen between 3% and 14%.

"This (agent) absolutely improves diagnostic imaging of focal live lesions," Hammerstingl said. "With this, we have a really specific agent that is targeted to the hepatocytes. Also we have the hepatobiliary excretion, so we get some information on function, and this gives us more specificity on the disease itself."

Primovist, injected manually or by power injector, is taken up by hepatocytes and excreted unmetabolized up to 50% via the kidneys and 50% via bile. The liver-specific phase appears in T1-weighted MR images about 20 minutes after injection. In the meantime, dynamic imaging can be used to generate MR cholangiograms of the arterial, venous, and equilibrium phases.

"Surgeons need to know as much as they can about the arterial supply, and this provides that information," Hammerstingl said.

Upon arrival at the liver, Primovist is selectively absorbed by normal hepatocytes. The enhancement of healthy but not diseased tissue provides a bright background against which cysts, metastases, and the majority of hepatocellular carcinomas stand out.

"For malignant lesions that have no hepatocytes, we have a really sharp margin," she said. "They are hypointense compared with the hyperintense parenchyma. So we have dark spots in the liver depicted best on static delayed imaging."

Primovist was approved by the European Union in September 2004 and is expected to begin shipping to European physicians within several weeks.