MRI contrast agents

Abstract

Pharmacologic agents used in the context of a cardiovascular magnetic resonance imaging examination can be divided into three main groups: contrast agents, stress-testing agents (dobutamine, adenosine, regadenoson, dipyridamole), and agents used for treatment of hypersensitivity reactions. The safety of stress agents will be elaborated in the chapter on ischaemic heart disease. This chapter will focus on contrast agents and briefly touch upon medications used in the setting of hypersensitivity reactions. Contrast agents are used to further augment tissue contrast and have become an integral component of cardiovascular imaging. These agents typically exert strong T1 shortening (gadolinium or manganese chelates, positive contrast) or T2 shortening (iron oxide particles, negative contrast). In some cases, very small iron particles may produce enhancement on either T1- or T2-weighted pulse sequences. The common factor lies in the paramagnetic properties of the material when exposed to an external magnetic field. The largest group of compounds consists of gadolinium-based contrast agents (GBCAs). Since the first description of nephrogenic systemic fibrosis in patients with renal insufficiency in 2000, and subsequent alerts by the US Food and Drug Administration and the European Medicines Association, interest in the safety of GBCAs has increased, along with concerted efforts to seek alternative contrast agents. Overall however, GBCAs are well tolerated.