Noninvasive Coronary Angiography Using Computed Tomography

Abstract

Irect visualization of the epicardial coronary arteries is necessary to confirm the presence and/or focal severity of coronary luminal disease. For nearly 50 years,1 invasive coronary arteriography has been the refer- ence standard for defining epicardial coronary artery disease. While conventional coronary arteriography provides for ex- ceptional spatial resolution and a general "road map" of the coronary system for catheter-based or surgical interventions, it is expensive, has a small but definite risk of complications, and requires either a brief hospitalization or a period of observation for several hours after the procedure in a special- ized monitored unit. For many patients with known or suspected luminal coronary disease, a convenient, noninva- sive, and safe means to perform coronary angiography would likely be of significant clinical and economic benefit. See p 2051 Electron beam (computed) tomography (EBT) has for some time been the only well-validated computed tomogra- phy (CT)-based imaging method that could reliably charac- terize cardiac mechanics and perfusion and provide insight into coronary atherosclerosis. 2 The latter was accomplished initially by defining coronary artery calcification (CAC) and its relationship to atherosclerotic plaque. 3 However, since the initial publications by Achenbach et al4 and Schmermund et al,5 EBT has been investigated increasingly as a means to perform noninvasive three-dimensional (3D) arteriography of the large epicardial coronary arteries, to examine coronary artery bypass grafts,6 and to characterize coronary artery anomalies.7 The published sensitivity and specificity of EBT for obstructive coronary disease as compared with invasive coronary arteriography has ranged from 85% to 90%. Recent changes in protocols to perform 1.5-mm slice imaging as opposed to the traditional 3.0-mm slice imaging, as well as development of improved post-processing methods, have further enhanced the robustness of the method and provided more reliable and more complete epicardial artery interroga- tion (personal experience and personal communication, Dr Matthew Budoff, Harbor UCLA Medical Center, Los Ange- les, Calif, 2002). Improvements in traditional CT imaging have likewise been far from slow, especially in the past several years, and have challenged the dominance of EBT in the cardiac imaging arena. Spiral or helical CT was plagued for years with x-ray source rotational speeds 10 times slower than EBT, and thus was not able to avoid image blurring due to cardiac motion. Additionally, single or even dual slice imag- ing with the older versions of spiral CT scanners required two or more breathholds just to complete thin sectioning of the heart.