Coronary artery computed tomographic angiography (CTA) demands specialized contrast injection techniaues to optimize enhancement of the coronary vasculature while minimizing artifact. An overview of the theories behina contrast injection protocols in CTA, the metrics that are currently employed to assess the guality of contrast injection, and the variables affecting contrast enhancement will be presented as an introduction to bolus geometry. The current application of these theories will be discussed in moaifications of injection protocols, opinions on contrast media selection and timing methods, specialized indications for cardiac CT, and future developments.
In recent years, multidetector computed tomography (CT) technology has advanced rapidly as commercial scanners have progressed from 4- to 16-to 64-detector rows, making coronary CT angiography (CTA) a clinical reality. In addition to providing better spatial resolution, multidetector CT scanners are significantly faster, resulting in shorter breath-hold requirements, reduced motion artifacts, and decreased contrast volume requirements when compared with single-detector-row helical scanners or conventional nonhelical scanners. The advent of 64-slice CT promises not only to enhance the utility of coronary CTA in a broad range of patients, but also to eliminate the need for conventional, invasive diagnostic coronary angiography in an appropriately selected population of patients (Figure 1).
The effectiveness of multidetector CTA in assessing coronary artery pathology is supported by a growing number of research reports that detail various techniques in the clinical setting.17 Among the consensus findings of these and other studies is that optimized contrast injection protocols are critical in providing uniform enhancement of the coronary arteries for diagnostic accuracy.8" This article provides an overview of the theories behind contrast injection protocols in CTA, the metrics currently employed to assess the quality of contrast injection, and the recognized variables affecting contrast enhancement. Modifications of injection protocols, opinions on contrast media selection and timing methods, specialized indications for cardiac CT, and future developments in customized injection protocols will be discussed.