Gd-EOB-DTPA-Enhanced MRI versus Extracellular Contrast Medium-Enhanced MRI in Differentiation of Metastatic from Benign Liver Lesions

Introduction

Metastatic liver disease is a common cause of malignant liver lesions worldwide and is about 18–40 timesmore commonthan primary liver tumors. Therefore, surgeons require new imaging modalities that can accurately and concisely evaluate such malignant lesions. Complete surgical resection of liver metastases prolongs survival and often contributes to complete cure, especially in colorectal carcinomas. Differentiation of malignant focal hepatic lesions from benign ones remains a diagnostic challenge. However, to improve the diagnosis of such lesions, new methods for existing modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), angiography, and ultrasonography, are being developed. For hepatic metastases detection, CT during arterial portography (CTAP) has been accepted as the most sensitive imaging modality; however, its invasiveness and substantial false-positive rate limits its use in routine screening of liver metastasis. Nonspecific gadolinium chelates such as gadolinium diethylene triamine penta-acetic acid (Gd-DTPA), gadobutrol, and gadobenate dimeglumine, which distribute in the extracellular fluid space, are currently most commonly employed extracellular contrast media (ECCM). ECCM are most effective during the dynamic phase of contrast enhancement when differential blood flow between the tumor and normal liver parenchyma leads to characteristic lesion enhancement patterns. Furthermore, dynamic contrast-enhanced MR study after a bolus injection of ECCM added information to nonenhanced MRI study and improved distinction between benign and malignant liver lesions. Previous reports have indicated that the sensitivity of non- and ECCM-enhanced MRI is superior to contrast-enhanced CT and is comparable or slightly inferior than CTAP for the detection of liver metastasis. With recent advances in MRI contrast media, MRI may become superior to CTAP for the diagnosis of liver lesions. MRI has some advantages over CT such as no risk from radiation exposure and no adverse reaction to iodinated contrast media. Indeed, MRI is rapidly evolving as the primary imaging modality for the detection and characterization of focal liver lesions. Liver-specific contrast media such as Gd-EOB-DTPA (Primovist®, Bayer Schering Pharma, Berlin, Germany), which combines dynamic and hepatocyte-specific imaging in one examination, are more helpful in detecting and accurately characterizing focal liver lesions. In this article, we present an overview of the diagnostic potentials of ECCM- and Gd-EOB-DTPA-enhanced MRI of the liver in patients with liver metastases to differentiate metastatic from benign liver lesions.

Abstract

Suitable resection of liver metastases improves survival and often leads to complete cure, especially in colorectal carcinomas. Accurate diagnosis of liver metastasis is important to assess the extent of hepatic resections. Liver metastases are often small and multiple, and intermingled with benign focal lesions, such as hemangiomas and cysts. Therefore, differentiating metastatic tumors from focal benign lesions is important.Magnetic resonance imaging (MRI) is well recognized as one of themost sensitive modalities for depicting liver metastatic tumors. Dynamic MRI using nonspecific extracellular contrast media (ECCM) has been shown to be superior to noncontrast-enhanced MRI for depicting liver metastases. Dynamic ECCM-enhanced MRI can show vascularity and interstitium of focal hepatic lesions. Gadolinium ethoxybenzyl diethylene triamine penta-acetic acid (Gd-EOB-DTPA, Primovist®, Bayer Schering Pharma, Berlin, Germany) is a hepatocyte-specific contrast medium specifically taken up in the delayed phase, thereby providing increased lesion–liver contrast not achievable with ECCM. Furthermore, Gd-EOB-DTPA can demonstrate enhancement characteristics and vascularity of liver lesions during the dynamic arterial, portal, and late phases after a bolus injection. Most liver metastases show a hypovascular pattern in the arterial–portal phase and hypointense pattern in the hepatocyte-specific phase of Gd-EOB-DTPA-enhanced MRI. Small hemangiomas, abscesses, and inflammatory pseudotumors are sometimes difficult to differentiate from metastatic tumors on MRI. This article reviews the current literature on Gd-EOB-DTPA-enhanced MRI versus ECCM-enhanced MRI in differentiating metastatic from benign liver lesions.

Keywords

Gd-EOB-DTPA, Primovist, ECCM, liver metastasis, MRI, focal liver lesion