Non-Gadolinium-Based MRI Contrast Agents

Abstract

Contrast agents for magnetic resonance imaging based on metal ions other than gadolinium(III) including manganese(II), manganese(III), iron(III) and copper(II), have been investigated over the past decade. Although the intrinsic properties of these metal ions tend to make these agents less attractive than gadolinium(III)-based agents, the large volume of literature on the biochemistry of these metal ions has allowed for the development of viable contrast agents. Agents specific for tissues such as the liver, pancreas, adrenals, cancerous tumors, and even the insides of cells and neuronal tracts as well as non-specific agents have been developed and tested in animal models. Two manganese (II) -based agents, the liver-specific agent manganese(II)-dipyridoxal diphosphate (Teslascan(R)) and an oral agent containing manganese(II) chloride (LumenHance(R)), and one ferric ammonium citrate-containing oral agent (FerriSeltz(R)) are available clinically for human use. Information on the toxicity, relaxivity, image enhancement, and tissue specificity of agents is discussed here. In addition to agents designed for use in living systems, contrast agents that measure pH and redox reactions in non-living systems have also been investigated and will be discussed. [References: 178]