Since approval of the first magnetic resonance (MR) contrast agent was granted in 1988, there has been remarkable growth in the utilization of intravenous gadolinium (Gd)-based agents. Currently it is estimated that nearly half of all MR studies performed are contrast-enhanced. Despite containing a toxic heavy metal, these agents have proven to be not only an effective diagnostic adjunct to non-enhanced MRI, but also remarkably well tolerated and safe. As a result, conventional wisdom has been that MR contrast media are "biologically inert," a notion that is clearly false. Ultimately, it is the radiologist's responsibility to understand the potential adverse effects of Gd-based agents and the special situations in which they are likely to occur; however, the basic pharmacology of contrast agents is generally not included in medical school curricula or formally taught in residency. The purpose of this review is to discuss the mechanism of action of MR contrast agents and relevant aspects of their clinical pharmacology, including effects on the cardiovascular and renal systems, potential laboratory errors, and special situations involving women and children. We also briefly discuss the issue of nephrogenic systemic fibrosis (NSF).

Compared with precontrast MR imaging, postcontrast MR imaging with Gd-EOB-DTPA demonstrated improved sensitivity for lesion detection in the majority of blinded readers, with no substantial adverse events.

CT and MRI performed similarly; both had lower staging accuracy than in prior single-institution studies. Accuracy of FIGO clinical staging was higher than previously reported. The temporal data suggest that FIGO clinical staging was influenced by CT and MRI findings.

Three patterns of enhancement of hemangiomas were observed. High signal intensity on T2-weighted images provided complementary information.

The detection of adrenal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance (MR) imaging is often useful for characterizing adrenal masses. Adrenal masses can be classified into various groups on the basis of the presence of intracellular lipid, macroscopic fat, hemorrhage, and cystic changes and the vascularity and shape of the tumor. These imaging features can be used by the radiologist to suggest or confirm a diagnosis for most adrenal masses, including adenoma, hyperplasia, simple and complicated cysts, lymphangioma, myelolipoma, pheochromocytoma, hemorrhage, cortical carcinoma, neuroblastoma, lymphoma, and metastases. Adenomas and metastases are common, and a decrease in signal intensity on out-of-phase images can be used to differentiate between them. Carcinoma is a possible diagnosis if that decrease in signal intensity is heterogeneous. Benign disease is diagnosed if macroscopic fat or a homogeneous cystlike lesion is seen. Recognition of the typical MR imaging features is important because it often changes the treatment approach and may obviate surgery.

Although US had the best diagnostic performance in depicting HCC on a patient-by-patient basis and was substantially better than were MR imaging and CT (which had nearly equivalent diagnostic performances), CT, US, and MR imaging performed similarly on a lesion-by-lesion basis. Small tumor nodules were the most common cause of missed HCCs with all tests. PET did not depict any HCCs.

The advent of gadolinium-based “hepatobiliary” contrast agents offers new opportunities for diagnostic MRI and has triggered a great interest for innovative imaging approaches to the liver and bile ducts. In this review article we will discuss the imaging properties of the two gadolinium-based hepatobiliary contrast agents currently available in the USA, gadobenate dimeglumine and gadoxetic acid, as well as important pharmacokinetic differences that affect their diagnostic performance. We will review potential applications, protocol optimization strategies, as well as diagnostic pitfalls. A variety of illustrative case examples will be used to demonstrate the role of these agents in detection and characterization of liver lesions as well as for imaging the biliary system. Changes in MR protocols geared towards optimizing workflow and imaging quality will also be discussed. It is our aim that the information provided in this article will facilitate the optimal utilization of these agents, and will stimulate the reader‘s pursuit of new applications for future benefit.

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