Interobserver agreement for the detection of atherosclerotic plaque in coronary CT angiography: comparison of two low-dose image acquisition protocols with standard retrospectively ECG-gated reconstruction

We compared the interobserver variability concerning the detection of calcified and non-calcified plaque in two different low-dose and standard retrospectively gated protocols for coronary CTA. 150 patients with low heart rates and less than 100 kg body weight were randomised and examined by contrast-enhanced dual-source CT coronary angiography (100 kV, 320 mAs). 50 patients were examined with prospectively ECG-triggered axial acquisition, 50 patients with prospectively ECG-triggered high pitch spiral acquisition, and 50 patients using spiral acquisition with retrospective ECG gating. Two investigators independently analysed the datasets concerning the presence of calcified and non-calcified plaque on a per-segment level. Mean effective dose was 1.4 +/- 0.2 mSv for axial, 0.8 +/- 0.07 mSv for high-pitch spiral, and 5.3 +/- 2.6 mSV for standard spiral acquisition (P < 0.0001). In axial acquisition, interobserver agreement concerning the presence of atherosclerotic plaque was achieved in 650/749 coronary segments (86.8%). In high-pitch spiral acquisition, agreement was achieved in 664/748 segments (88.8%, n.s.). In standard spiral acquisition, agreement was achieved in 672/738 segments (91.0%, P < 0.0001). Interobserver agreement was significantly higher for calcified than for non-calcified plaque in all data acquisition modes. Low-dose coronary CT angiography permits the detection of coronary atherosclerotic plaque with good interobserver agreement. aEuro cent Low-dose CT protocols permit coronary plaque detection with good interobserver agreement. aEuro cent Image noise is a major predictor of interobserver variability. aEuro cent Interobserver agreement is significantly higher for calcified than for non-calcified plaque.