Contrast Agents

Abstract

Magnetic resonance imaging has been recognized for its superior anatomic detail, soft-tissue contrast resolution, multiplanar capability, and noninvasive nature since the early 1980s, when it was introduced into clinical practice. These attributes have helped to establish MRI as the de facto gold standard for diagnosing most diseases of the central nervous system. Since the initial expectations of the capabilities of this technology were so high, it was felt that diagnostic pharmaceuticals to enhance image contrast would not be useful. As clinical experience using MR broadened, however, this supposition was challenged. It was found that in as many as 12% of brain tumors, the MR properties of tumor and normal brain parenchyma were sufficiently similar to allow disease to go undetected in standard T1- and T2-weighted images. The differential change in signal intensity provided by an MR contrast agent proved beneficial in resolving these ambiguities and improved the specificity of MR by highlighting regions of blood/brain barrier breakdown, by identifying the presence or absence of perfusion and/or abnormal vascularity, and by distinguishing tumor from associated edema.