Tomographic (plaque) imaging: state of the art

Tomographic coronary artery plaque imaging is possible noninvasively using x-ray computed tomography (CT) and magnetic resonance imaging (MRI). The pathophysiology of coronary plaque disease is one of repeated inflammation and repair. Imaging of coronary artery calcium, a consequence of this process, is possible using CT, whereas MRI has the potential to examine the lipid and fibrous components of plaque acquisition and 3-dimensional slice registration. Quantitation of coronary artery calcium has been validated using electron-beam CT [EBCT], a unique device that images the entire heart in a single breathold from rapid [100 msec] tomographic scans done in synchrony with the heart cycle. Current mechanical CT devices require 300 to 500 msec per scan and acquire hundreds of tomographic images that then must be retrospectively separated to the required phase of the heart cycle. There are limited correlations with calcium scoring by EBCT versus mechanical CT and the later device has a limitation in situations of low plaque volume and necessitates increased radiation exposure to the patient. MRI has been shown to have the potential to define plaque composition ex vivo or in the aorta, but studies of the heart arteries are so far very limited. Widespread utilization of noninvasive plaque imaging requires that the studies be done consistently and reproducibly. The training of the interpreting physicians is of paramount concern.