Feasibility of low-dose coronary CT angiography: first experience with prospective ECG-gating

Abstract

To determine the feasibility of prospective electrocardiogram (ECG)-gating to achieve low-dose computed tomography coronary angiography (CTCA). Forty-one consecutive patients with suspected (n = 35) or known coronary artery disease (n = 6) underwent 64-slice CTCA using prospective ECG-gating. Individual radiation dose exposure was estimated from the dose-length product. Two independent readers semi-quantitatively assessed the overall image quality on a five-point scale and measured vessel attenuation in each coronary segment. One patient was excluded for atrial fibrillation. Mean effective radiation dose was 2.1 ± 0.6 mSv (range, 1.1–3.0 mSv). Image quality was inversely related to heart rate (HR) (57.3 ± 6.2, range 39–66 b.p.m.; r = 0.58, P < 0.001), vessel attenuation (346 ± 104, range 110–780 HU; r = 0.56, P < 0.001), and body mass index (26.1 ± 4.0, range 19.1–36.3 kg/m²; r = 0.45, P < 0.001), but not to HR variability (1.5 ± 1.0, range 0.2–5.1 b.p.m.; r = 0.28, P = 0.069). Non-diagnostic CTCA image quality was found in 5.0% of coronary segments. However, below a HR of 63 b.p.m. (n = 28), as determined by receiver operator characteristic curve, only 1.1% of coronary segments were non-diagnostic compared with 14.8% with HR of >63 b.p.m. (P < 0.001). This first experience documents the feasibility of prospective ECG-gating for CTCA with diagnostic image quality at a low radiation dose (1.1–3.0 mSv), favouring HR <63 b.p.m.