Imaging is reliant upon the contrast between different body elements, which may be present naturally or may require the introduction of extrinsic contrast agents. Since the 1920s, the use of contrast agents has been refined to enhance the diagnostic potential of multiple imaging modalities. Contrast agents are a vital part of diagnosis and treatment algorithms involving image guidance. Given the wealth of contrast agents on the market, a basic understanding of the various types is critical for budding interventional radiologists who need to use such agents judiciously on a daily basis. Such contrast agents may be administered intravenously, intraarterially, intrathecally, orally, via inhalation, transrectally, or via indwelling tubes or catheters cannulating a specific viscus. In this chapter, we review the key categories, contraindications, and alternatives for such agents, with special attention to their use in an interventional radiology (IR) practice.
