Dose Reduction and Image Quality Assessment in 64-Detector Row Computed Tomography of the Coronary Arteries Using an Automatic Exposure Control System

Objective: To evaluate dose reduction and image quality in coronary 64-slice multidetector computed tomography using an automatic exposure control system (AECs). Methods: A total of 101 patients were divided into 4 groups. Tube current was 600 and 800 mAs in groups A and B and adapted at 600 and 800 quality-reference mAs using an AECs in groups C and D. Effective dose and organ-equivalent dose were evaluated. Image noise was quantified as standard deviation of air-space attenuation. Two observers assessed technical adequacy and image quality using a 4-point scale. Results: Effective dose ranged from 8.6 mSv (group C) to 15 mSv (group 13) with significant dose reduction for examinations perfornied at 600 mAs (21.7%) and 800 mAs (29.4%). Contribution of organ-equivalent doses showed higher exposure for lungs (42%) and breast (22%). Noise was significantly higher in groups studied with AECs. Larger coronary segments resulted in higher image quality scores without differences between groups. Conclusion: Automatic exposure control systems provides images of diagnostic quality with substantial dose reduction.