Update: safety, new applications, new MR agents

In the last decade, i.v. contrast media use in magnetic resonance imaging (MRI) of the central nervous system has become well established. Three agents are currently available in the United States: gadopentetate dimeglumine (Magnevist), gadodiamide (Omniscan), and gadoteridol (ProHance). At a dose of 0.1 mmol/kg, for which all three agents are approved, the contrast effect is equivalent. The agents differ on the basis of stability in vivo, osmolality, and charge. A single agent (ProHance) is approved for high-dose administration (0.3 mmol/kg). The basis of this approval is due in part to the high stability of the agent and thus lower potential for toxicity from long-term heavy metal deposition. Clinical experience, combined with new developments in MR technology, continue to expand applications for these agents. Improved detection of metastatic disease to the brain has been demonstrated in multiple clinical trials with high-dose contrast administration. High dose may also play an important role in brain infection and infarction, providing improved recognition of blood-brain barrier disruption and thus disease activity. First-pass studies make possible the evaluation of regional cerebral blood volume with high intrinsic spatial resolution. The availability of new instrumentation, together with the use of high contrast dose, have improved the quality and clinical utility of these studies. Research is ongoing in the development of new agents, both with greater tissue selectivity and improved safety profile. Chelates of dysprosium, in addition to gadolinium, are receiving attention for potential clinical application in first-pass imaging.