Optimizing image quality in low-dose, low-iodine coronary CT angiography: a comparative study of iterative reconstruction strengths

This study aimed to evaluate the impact of varying strengths of the Advanced Modeled Iterative Reconstruction (ADMIRE) algorithm on image quality in coronary CT angiography (CCTA) performed at 70 kVp tube voltage and low-concentration iodine contrast agent (iomeprol 300 mgI/ml). A prospective study included 107 patients undergoing CCTA, divided into two independent groups, Group A ( n = 52) and Group B ( n = 55). Group A utilized 70 kVp and automatic tube current modulation (ATCM) with an injection dose of 1.0 ml/kg at a flow rate of 5.0 ml/s using 300 mgI/ml iodine contrast. Images were reconstructed using FBP (A0), ADMIRE 1 (A1), ADMIRE 3 (A3), and ADMIRE 5 (A5). Group B used 120 kVp and 350 mgI/ml iodine contrast with the same scanning parameters, reconstructing only FBP (B0). Objective image quality was assessed through CT values, signal-to-noise ratio (SNR Coronary ), contrast-to-noise ratio (CNR coronary to fat ), and image noise (SD). Two radiologists independently evaluated coronary CTA image quality using a 5-point Likert scale. No significant differences in age, sex, BMI, or HR were observed between groups (all p > 0.05). Compared with Group B, Group A showed a 72.4% reduction in CTDIvol (12.28 ± 3.68 mGy vs. 44.44 ± 12.75 mGy; p < 0.001) and an 18.6% reduction in IU ( p < 0.01). No significant differences in coronary CT values were observed among A0–A5 ( p > 0.05). Within the “dual-low” Group A, image noise decreased significantly as the ADMIRE reconstruction strength increased from A0 to A5 (aortic root SD: 69.71 to 41.19, p < 0.001), while SNR Coronary and CNR coronary to fat improved markedly ( p < 0.001), and subjective image quality scores increased significantly ( p < 0.001). Notably, images reconstructed with the highest strength A5 algorithm showed better objective SNR Coronary /CNR coronary to fat and subjective scores than standard dose B0 images; images reconstructed with the A3 algorithm exhibited comparable image quality compared to B0 images. The combination of 70 kVp and low-concentration iodine contrast (300 mgI/ml) with ADMIRE reconstruction can significantly reduce radiation and iodine burden while achieving comparable or better image quality than standard dose (SDCT). ADMIRE 3 meets traditional standards, and ADMIRE 5 offers further optimization. This study confirms the feasibility of “dual-low” combined with high-strength iterative reconstruction techniques in clinical practice, providing optimized parameters for CCTA examinations.