Multidetector-row CT of the heart

Coronary artery disease (CAD) remains the leading cause of death in western nations. The standard of reference for diagnosis of CAD is coronary catheter angiography. In the year 1999 more than 1.83 million cardiac catheter examinations were performed in the United States [1]. The greatest advantage of catheter angiography is its high spatial resolution and the option of directly performing interventions, such as balloon dilatation or coronary stenting. Only one third of all coronary catheter examinations in the United States were performed in conjunction with an interventional procedure (percutaneous transluminal coronary angioplasty [PTCA]), however, whereas the rest were performed for mere diagnostic purposes (ie, for verifying the presence and degree of CAD only) [1]. Accordingly, a reliable, noninvasive tool for imaging of the coronary arteries and for early diagnosis of CAD is highly desirable. Imaging of the heart has always been technically challenging, because of the heart's continuous motion. CT imaging of the heart moved into the diagnostic realm by the introduction of electron-beam CT [2] and multidetector-row CT (MDCT) [3,4] and the development of ECG-synchronized scanning and reconstruction techniques [5]. These modalities allow for faster volume coverage and higher spatial and temporal resolution. The introduction of MDCT especially has greatly benefited cardiovascular CT imaging applications. The speed of image acquisition shortens breathhold and examination times for the patient and reduces the amount of contrast media needed for high and consistent vascular enhancement [5-9]. With the advent of 16-slice MDCT scanners submillimeter resolution of substantial anatomic volumes is routinely achieved [8]. Until recently, cardiac CT applications were almost exclusively directed at the detection and quantification of coronary calcium. It is increasingly recognized, however, that the diagnostic value of CT coronary calcium measurements alone is limited. Contrast-enhanced MDCT may effectively address these limitations. Investigation of the heart with submillimeter spatial resolution and a temporal resolution of 200 milliseconds now enables accurate, high-resolution morphologic evaluation of both the myocardium and the coronary arteries. Because of the cross-sectional nature of CT, the vessel wall can be evaluated. The potential of this technique for noninvasive identification of vulnerable atherosclerotic lesions, which may have a higher propensity to trigger acute coronary syndromes than stable, calcified plaques, is an area of active research. MDCT may become a valuable tool for noninvasive atherosclerosis imaging.