MR imaging in the evaluation of hepatic metastases

Optimal detection of focal hepatic lesions in patients with metastases can alter patient management and result in significant cost savings by reducing the number of unnecessary laparotomies for unresectable disease. Liver-specific MR imaging contrast agents (reticuloendothelial and hepatobiliary agents) offer greater lesion-to-liver contrast than the conventional extracellular fluid space MR imaging contrast agents (gadolinium chelates), which have a nonspecific distribution. For the detection of hepatic metastases, although the work of Seneterre et al suggests that the accuracy of ferumoxide-enhanced MR imaging is equivalent to that of CTAP, other studies find CTAP to be superior. Comparisons of reticuloendothelial agents and hepatobiliary agents for imaging liver metastases are lacking in the literature. Further studies comparing MR imaging enhanced with liver-specific contrast agents to CTAP are needed to determine if hepatic MR imaging can replace CTAP for the preoperative evaluation of hepatic metastases. For the characterization of focal liver lesions, MnDPDP and ferumoxides have been added to the small list of FDA-approved contrast agents, and both can help to increase diagnostic specificity. Two of the hepatobiliary agents which are not yet approved, Gd-BOPTA and Gd-EOB-DTPA, have the potential of characterizing liver lesions during dynamic contrast enhancement (similar to Gd-DTPA) and during the hepatocyte phase (similar to MnDPDP), and may increase the detection of focal liver lesions.