Ultra-low 70-kV cardiac CT angiography in neonates: a comparative dose-optimized approach with preserved image quality.

OBJECTIVE: To evaluate the feasibility of ultra-low tube voltage (70 kV) cardiac CT angiography (CTA) with weight-adapted iodine delivery in neonates and to compare image quality, coronary visibility, radiation exposure, and iodine delivery with those of a conventional 80-kV protocol. METHODS: This retrospective study included 125 neonates with congenital heart disease who underwent prospectively ECG-triggered cardiac CTA using a 256-row CT scanner. Patients were divided into an 80-kV group reconstructed with 50% adaptive statistical iterative reconstruction-V (ASIR-V) (n = 61) and a 70-kV group reconstructed with 70% ASIR-V (n = 64). Both protocols used standardized weight-adapted iodine delivery (450 mg I/kg). Subjective and objective image quality, coronary artery visibility, radiation dose, and iodine delivery were compared between groups. RESULTS: Overall interobserver agreement for subjective image quality assessment was excellent (κ = 0.815). Subjective image quality scores were comparable between the two groups across most coronary segments, with no significant differences in overall image quality (3.98 ± 1.04 vs. 3.95 ± 1.05, P = 0.545). Objective image quality parameters, including CT attenuation, image noise, signal-to-noise ratio, and contrast-to-noise ratio, also showed no significant differences between groups (all P > 0.05). Coronary artery visibility remained high in both groups, with overall visibility rates exceeding 89%. Importantly, distal coronary segments remained diagnostically assessable in approximately 75% of cases under the 70-kV protocol. Compared with the 80-kV protocol, the 70-kV protocol achieved a 24% reduction in effective radiation dose (0.32 ± 0.05 vs. 0.42 ± 0.06 mSv, P < 0.001) without increasing iodine delivery. CONCLUSIONS: Ultra-low tube voltage (70 kV) cardiac CT with weight-adjusted iodine delivery is feasible for neonatal imaging and can substantially reduce radiation exposure while preserving coronary artery image quality and visibility. This approach may help achieve a more balanced trade-off among image quality, radiation dose, and contrast administration in neonatal cardiac CT examinations.