Estimated Radiation Dose Associated With Cardiac CT Angiography

Abstract

CONTEXT: Cardiac computed tomography (CT) angiography (CCTA) has emerged as a useful diagnostic imaging modality in the assessment of coronary artery disease. However, the potential risks due to exposure to ionizing radiation associated with CCTA have raised concerns. OBJECTIVES: To estimate the radiation dose of CCTA in routine clinical practice as well as the association of currently available strategies with dose reduction and to identify the independent factors contributing to radiation dose. DESIGN, SETTING, AND PATIENTS: A cross-sectional, international, multicenter, observational study (50 study sites: 21 university hospitals and 29 community hospitals) of estimated radiation dose in 1965 patients undergoing CCTA between February and December 2007. Linear regression analysis was used to identify independent predictors associated with dose. MAIN OUTCOME MEASURE: Dose-length product (DLP) of CCTA. RESULTS: The median DLP of 1965 CCTA examinations performed at 50 study sites was 885 mGy x cm (interquartile range, 568-1259 mGy x cm), which corresponds to an estimated radiation dose of 12 mSv (or 1.2 x the dose of an abdominal CT study or 600 chest x-rays). A high variability in DLP was observed between study sites (range of median DLPs per site, 331-2146 mGy x cm). Independent factors associated with radiation dose were patient weight (relative effect on DLP, 5%; 95% confidence interval [CI], 4%-6%), absence of stable sinus rhythm (10%; 95% CI, 2%-19%), scan length (5%; 95% CI, 4%-6%), electrocardiographically controlled tube current modulation (-25%; 95% CI, -23% to -28%; applied in 73% of patients), 100-kV tube voltage (-46%; 95% CI, -42% to -51%; applied in 5% of patients), sequential scanning (-78%; 95% CI, -77% to -79%; applied in 6% of patients), experience in cardiac CT (-1%; 95% CI, -1% to 0%), number of CCTAs per month (0%; 95% CI, 0%-1%), and type of 64-slice CT system (for highest vs lowest dose system, 97%; 95% CI, 88%-106%). Algorithms for dose reduction were not associated with deteriorated diagnostic image quality in this observational study. CONCLUSIONS: Median doses of CCTA differ significantly between study sites and CT systems. Effective strategies to reduce radiation dose are available but some strategies are not frequently used. The comparable diagnostic image quality may support an increased use of dose-saving strategies in adequately selected patients.