Segment-Level Evaluability of Dedicated Non-ECG-Gated Coronary CT Angiography: Associations with Calcification, Heart Rate, Vessel Territory, and Caliber

Background/Objectives: Dedicated coronary CT angiography (CCTA) without physical electrocardiographic gating may simplify acquisition, but segment-level interpretability may vary across the coronary tree. We evaluated coronary segment evaluability and factors associated with non-evaluability on dedicated non-ECG-gated CCTA. Methods: This retrospective single-center study included 320 patients and 3739 anatomically present coronary segments with a reference diameter of at least 1.5 mm. Evaluability required confident classification of diameter stenosis as <50% or ≥50%. Segment calcification was graded separately using a prespecified visual scale as none, mild, moderate, or severe. Patient-clustered generalized estimating equations used a binomial distribution, logit link, exchangeable working correlation, and robust standard errors. Results: Overall, 3378 segments (90.3%) were evaluable. All included segments were evaluable in 118/320 patients (36.9%); 202/320 (63.1%) had at least one non-evaluable segment and 111/320 (34.7%) had at least one proximal/mid non-evaluable segment. Examination success was 320/336 (95.2%). When 182 observed eligible segments from the 16 globally non-diagnostic examinations were included as non-evaluable, segment evaluability was 3378/3921 (86.2%); an additional 18-segment worst-case boundary yielded 3378/4027 (83.9%). Evaluability declined from 93.4% without calcification to 88.8%, 84.3%, and 74.3% with mild, moderate, and severe calcification. Adjusted odds ratios for non-evaluability were 1.95 (95% CI, 1.46–2.60), 3.13 (2.18–4.49), and 6.53 (4.39–9.71), respectively, versus no calcification. Higher heart rate (per 10 beats/min: OR, 1.52; 95% CI, 1.36–1.69) and right coronary artery location (OR, 1.56; 95% CI, 1.20–2.02) were associated with non-evaluability, whereas larger reference diameter was associated with lower odds (per 1 mm: OR, 0.69; 95% CI, 0.53–0.89). Conclusions: Most included coronary segments were evaluable on dedicated non-ECG-gated CCTA, but interpretability varied with calcification, heart rate, vessel territory, and caliber. These findings characterize segment-level feasibility and do not establish diagnostic accuracy, equivalence to ECG-gated CCTA, or a clinical eligibility threshold.