Use of automatic exposure control in multislice computed tomography of the coronaries:: comparison of 16-slice and 64-slice scanner data with conventional coronary angiography

Objective: To evaluate the radiation- dose- reduction potential of automatic exposure control ( AEC) in 16- slice and 64- slice multislice computed tomography ( MSCT) of the coronary arteries ( computed tomography angiography, CTA) in patients. The rapid growth in MSCT CTA emphasises the necessity of adjusting technique factors to reduce radiation dose exposure. Design: A retrospective data analysis was performed for 154 patients who had undergone MSCT CTA. Group 1 ( n = 56) had undergone 16- slice MSCT without AEC, and group 2 ( n = 51), with AEC. In group 1, invasive coronary angiography ( ICA) had been performed in addition. Group 3 ( n = 47) had been examined using a 64- slice scanner ( with AEC, without ECG- triggered tube current modulation). Results: In group 1, the mean ( SD) effective dose ( ED) for MSCT CTA was 9.76 ( 1.84) mSv and for ICA it was 2.6 ( 1.27) mSv. In group 2, the mean ED for MSCT CTA was 5.83 ( 1.73) mSv, which signifies a 42.8% dose reduction for CTA by the use of AEC. In comparison to ICA, MSCT CTA without AEC shows a 3.8- fold increase in radiation dose, and the radiation dose of CTA with AEC was increased by a factor of 1.9. In group 3, the mean ED for MSCT CTA was 13.58 ( 2.80) mSV. Conclusions: This is the first study to show the significant dose- reduction potential ( 42.8%) of AEC in MSCT CTA in patients. This relatively new technique can be used to optimise the radiation dose levels in MSCT CTA.