Integrated non-invasive imaging techniques

Abstract

The development of imaging techniques for the non-invasive detection of atherosclerosis answered the specific need of identifying vulnerable plaque in asymptomatic patients, verify the presence of atherosclerosis in patients at intermediate risk of coronary artery disease and, lastly, evaluate the results of previous coronary interventions. Coronary computed tomography angiography is the non-invasive technique that has been most widely used for these purposes. The technique mainly focuses on the presence of calcium in the walls of the coronary arteries. Whether or not coronary arterial calcification is part of the development of atherosclerosis, it occurs in small amounts in the early lesions and is found more frequently in advanced lesions and at an older age. Plaques rich in collagen and calcium, which can be depicted by coronary calcium scoring, are widely considered firm and stable, whereas soft atheromas containing a core of lipids and necrotic debris that are biologically "unstable" and therefore prone to rupture, cannot be visualised by calcium scoring or correctly assessed by coronary computed tomography angiography. In fact, the relation of arterial calcification to the probability of plaque rupture is unknown. There is no definite relationship between vulnerable plaque and coronary artery calcification in comparative studies with intravascular ultrasound. On the other hand, radiographically detected coronary artery calcium can provide an estimate of total coronary plaque burden but, due to arterial remodelling, calcium does not concentrate exclusively at sites with severe coronary artery stenoses. In any event, this technique has great potential for identification of atherosclerosis. A more established use of coronary computed tomography angiography is in the evaluation of patients after coronary interventions. The future also holds promise for imaging coronary artery atherosclerotic plaques using magnetic resonance. At the present time, the differentiation of coronary plaque components with magnetic resonance is limited by inadequate spatial resolution; however, promising research is ongoing and the role of magnetic resonance in the evaluation of patients with coronary artery disease will continue to grow as its utility and prognostic importance will be further defined.