EComment. Cardiac computed tomography angiography for evaluation of coronary artery bypass grafts

Abstract

Sahiner and colleagues [1] demonstrate the comparative efficacy of 16- vs 64-slice cardiac computed tomography (CT) angiography when assessing coronary artery bypass grafts. One of the major concerns regarding the increased use of cardiac CT angiography is the effective radiation dose received by patients. The widening indications and applications of cardiac CT angiography may mean patients undergo multiple studies during their lifetime. The improved spatial and temporal resolution achieved by 64-slice cardiac CT over 16-slice cardiac CT comes at the expense of an increased effective radiation dose. In a study comparing 16- and 64-slice cardiac CT angiography, despite strategies to reduce radiation dose including reduction in tube voltage and changing gating strategies, the effective dose for cardiac CT was 6.4±1.9 and 11.0±4.1 mSv with 16- and 64-slice CT, respectively [2]. The Society of Cardiovascular Computed Tomography promotes the “ALARA principle“, which states that the radiation dose to a patient should be Low As Reasonably Achievable. In other words, we should use the lowest optimal radiation dose possible to achieve a diagnostic image [3]. In this study there was a similar diagnostic accuracy for graft patency between 16- and 64-slice cardiac CT although the 16 slice was less accurate for detecting graft stenosis. All proximal anastomosis could be visualized using both techniques. Therefore in certain clinical scenarios, where the question to be answered depends on identifying the origin of grafts or patency of grafts, the use of 16-slice cardiac CT will provide diagnostic information at a lower radiation dose. Conflict of interest: none declared