Contrast Medium Injection Technique

Abstract

The general goal of intravenous contrast medium (CM) delivery in computed tomography (CT) is to achieve adequate enhancement of the organ or vessels within the anatomic territory of interest, synchronized with the CT acquisition. This apparently simple goal is increasingly difficult to achieve with rapidly and continuously evolving multiple detector-row CT (MDCT) technology. Given that acquisition times have substantially decreased with each new generation of MDCT scanners, correct scan timing and tailoring clinical injection protocols are ever more challenging and less forgiving. Thus, a working understanding of early contrast medium dynamics has become a prerequisite for the rational design of current and future injection strategies. The selection of CM type, CM iodine concentration, considerations regarding the interrelated effects of injection flow rates, CM injection duration and injection volume, new injection devices, and individual patient factors all have to be integrated to optimize acquisition of a diagnostically meaningful MDCT examination. The purpose of this chapter is to provide the reader with the basic tools for designing rational contrast medium injection protocols for various applications of thoracic MDCT. This will encompass a review of physiologic and pharmacokinetic principles, as well as a discussion of contrast media properties, injection devices and tools for accurate scan timing. Topics of current interest, including CM strategies for patients with chronic kidney disease (CKD) and low-kVp image acquisition, will be discussed. In addition, practical examples of injection protocols will be provided.