Coronary Angiography of Native Vessels

Abstract

Cardiac computed tomography (CT) is a robust technology for the non-invasive assessment for a spectrum of cardiovascular disease processes. This image modality has been used to provide assessment of atherosclerotic plaque burden and coronary artery disease risk through coronary calcium scoring for 20 years and CT angiography for over 10 years [1]. While electron beam tomography has been used to perform CT angiography (CTA) for well over a decade, this modality has been largely supplanted by multidetector computed tomography (MDCT) due to higher spatial resolution, improved slice thickness, and greater availability. MDCT scanners with x-ray tubes rotating fast enough to allow coronary artery imaging (500 milliseconds [ms] or less per rotation) became available in the late 1990s. The temporal resolution of MDCT is a little more than half the time it takes for the x-ray gantry to complete a 360 ◦ rotation around the patient when using half-scan reconstruction. Thus, typical rotation speeds are 330–420 ms (depending on vendor), so half-scan reconstruction results in rotation speeds of 200–250 ms. The nominal temporal resolution can be improved by a factor of 2–3 (depending on the heart rate) by segmented reconstruction techniques that combine projection data acquired during two or more cardiac cycles into one image. This has been done in two ways. Combining images from consecutive heartbeats is widely available on all current 64-detector systems (multisegment reconstruction). The Dual Source CT (Siemens, Erlangen, Germany) can also obtain similar temporal resolution by combining images from two detector arrays in the same heartbeat. In this way, current MDCT scanners can acquire up to 64 slices simultaneously with a maximum temporal resolution as low as 100 ms. Because of the high motion velocity of the coronary arteries, CT scanners must have temporal resolution of <50 ms to provide motion-free images of the beating heart. Since that level of temporal resolution is not yet available with current MDCT scanners, use of beta-blockers is routine. Most centers utilize oral beta-blockers prior to patient arrival at the scanning center if possible, and subsequent use of intravenous