Coronary CT angiography in the emergency department utilizing second and third generation dual source CT

Abstract

BackgroundCoronary computed tomography angiography (coronary CTA) allows efficient triage of low to intermediate risk patients with suspected acute coronary syndrome (ACS) in the emergency department (ED). Techniques for coronary CTA acquisition in the ED continue to evolve with the establishment of standardized scan protocols and the introduction of newer generations of CT hardware. ObjectivesTo evaluate qualitative and quantitative image quality and radiation dose exposure of coronary CTA acquired on 2nd versus 3rd generation dual source CT (DSCT) scanners using a standardized institutional scan protocol designed for the ED. MethodsA retrospective observational case-control study was performed of 246 ED patients referred to coronary CTA with suspicion of ACS (56.5% male; mean age 53.3 ± 11.6 years) between October 2013 and August 2015.123 consecutive patients were scanned on 3rd generation DSCT, and a cohort of 123 patients matched by age, BMI and heart rate were identified who had undergone 2nd generation DSCT imaging utilizing the same standard clinical protocol. Qualitative and quantitative image quality parameters and radiation exposures were evaluated. ResultsQualitative image quality was significantly higher using 3rd generation DSCT as compared to 2nd generation (p < 0.001). Mean attenuation in the proximal coronary arteries was also significantly higher on 3rd generation DSCT than for 2nd generation (586 HU vs. 426 HU in the left main coronary artery (LM), p < 0.001). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values, however, were lower in 3rd generation DSCT than 2nd generation (SNR 11.2 [9.9–13.4] vs 13.5 [11.0–15.5] and CNR 12.4 [10.9–14.8] vs 15.2 [12.8–17.9] in the LM, p < 0.001). Median effective dose was also lower for 3rd generation DSCT than for 2nd generation (2.9 [2.3–5.0] mSv and 3.7 mSv [2.5–5.7], respectively) although this trend did not reach statistical significance (p = 0.065). ConclusionQualitative image quality and mean CT attenuation values of the assessed coronary segments were significantly higher using 3rd generation DSCT. SNR and CNR were lower on 3rd generation DSCT, however this was accompanied by a trend toward lower radiation dose exposure when using the same standard institutional protocol.