AIMS: To evaluate the feasibility and image quality of coronary computed tomography angiography (CCTA) acquisition with a submillisievert fraction of effective radiation dose using model-based iterative reconstruction (MBIR) for noise reduction.
METHODS AND RESULTS: In 42 patients undergoing standard low-dose (100-120 kV; 450-700 mA) and additional ultra-low-dose CCTA (80-100 kV; 150-210 mA) reconstructed with MBIR, segmental image quality was graded on a four-point scale [(i): non-evaluative, (ii): good, (iii): adequate, and (iv): excellent]. Signal-to-noise ratio (SNR) was calculated dividing left main artery (LMA) and right coronary artery (RCA) attenuation by the aortic root noise. Over a wide range of body mass index (18-40 kg/m(2)), the estimated median radiation dose exposure was 1.19 mSv [interquartile range (IQR): 1.07-1.30 mSv] for standard and 0.21 mSv (IQR: 0.18-0.23 mSv) for ultra-low-dose CCTA (P < 0.001). The median image quality score per segment was 3.5 (IQR: 3.0-4.0) in standard CCTA vs. 3.5 (IQR: 2.5-4.0) in ultra-low dose with MBIR (P = 0.29). Diagnostic image quality (scores 2-4) was found in 98.7 vs. 97.8% coronary segments (P = 0.36). Introduction of MBIR for ultra-low-dose CCTA resulted in a significant increase in SNR (P < 0.001) for LMA (from 15 ± 5 to 29 ± 7) and RCA (from 14 ± 4 to 27 ± 6) despite 82% dose reduction.
CONCLUSION: Coronary computed tomography angiography acquisition with diagnostic image quality is feasible at an ultra-low radiation dose of 0.21 mSv, e.g. in the range reported for a postero-anterior and lateral chest X-ray.