Appropriate decision-making in the low to intermediate-risk subgroup of patients presenting with acute chest pain requires new tools. We postulate that perhaps the incorporation of coronary CTA can, by providing an anatomical window that defines the amount of atherosclerotic burden within the coronary tree, advance the risk-stratification algorithm in low to intermediate-risk acute chest pain in a cost-effective manner. In recent years, there has been much interest in noninvasive imaging techniques that allow direct visualization and assessment of the coronary arteries (Image A). The coronary tree is challenging to image due to the continuous motion of the coronary arteries. This motion necessitates both high spatial and temporal resolution. Recent advances in computed tomography (CT) techniques have made imaging of the coronary arteries possible. The introduction of electron-beam CT (EBCT) in 1984 first allowed for ECG-synchronized imaging of the heart. In 1998, the first multiple detector spiral CT (MDCT) system with 4 detector rows was introduced, allowing for greater volume of coverage with each rotation of the CT gantry than EBCT. 23 Since that time, gantry rotation times have decreased, resulting in improved temporal resolution. An increase in number of detectors has allowed for sub-millimeter spatial resolution. At this time, 64 slice MDCT (Image A) is considered the "state of the art" technology for performance of coronary CTA, although the next generation of scanners, including dual source and 256 slice MDCT are currently under evaluation. Several small studies in the literature have shown the utility of coronary CTA in the safe and rapid triage of low to intermediate-risk acute chest pain patients presenting to the ED24-29. One of the clinical advantages of the coronary CTA is that, unlike stress testing that can detect flow limiting stenosis but not CAD; it can detect flow limiting stenosis in addition to the presence or absence of coronary artery disease. The disadvantage of coronary CTA is the exposure to radiation.