Multidetector-Row Computed Tomography Coronary Angiography

onsiderable progress has recently been achieved in the field of noninvasive imaging of the coronary arteries by computed tomography (CT). Multidetector-row CT (MDCT) scanners are equipped with thinner detectors and have a shorter rotation time, which enables considerably faster volume coverage with a thinner slice width during a single breath hold. The entire heart volume can be covered with nearly isotropic spatial resolution. By using the retrospective ECG gating technique, cardiac CT imaging can be obtained during an arbitrary cardiac period with a data acquisition window that is shorter than the rotation time of the scanner. However, taking into consideration that the inherent cardiac motion is rather large and complicated, this data acquisition window is not sufficiently short. Therefore, it is not always possible to obtain an adequate quality image, irrespective of which phase of the cardiac cycle the image is reconstructed in. Several methods have been attempted to determine the optimal phase for image reconstruction. In patients with lower heart rates (HRs), some researchers recommend image reconstruction in the slow filling period, 1–4 and adequate image quality for evaluation of stenoses and plaques can be obtained.5–7 A similar phenomenon of better image quality for clinical use occurs in patients with lower HRs or those usingβ-blockers. 8 However,β-blockers are contraindicated in cases of congestive heart failure, atrioventricular block, or bronchial asthma, and the adverse reactions of contrast media can be severe in those usingβ-blockers. 9,10