Abstract
Background: Coronary calcification can lead to over-estimation of the degree of coronary stenosis.
Purpose: To evaluate whether thinner reconstruction thickness improves the diagnostic performance of 64-slice CT coronary angiography (CTCA) in angina patients with a positive calcium score.
Material and Methods: We selected 20 scans from a clinical study comparing CTCA to conventional coronary angiography (CCA) in stable and unstable angina patients based on a low number of motion artifacts and a positive calcium score. All images were acquired at 64×0.625 mm and each CTCA scan was reconstructed at slice thickness/increment 0.67 mm/0.33 mm, 0.9 mm/0.45 mm, and 1.4 mm/0.7 mm. Two reviewers blinded for CCA results independently evaluated the scans for the presence of significant coronary artery disease (CAD) in three randomly composed series, with ≥2 weeks in between series. The diagnostic performance of CTCA was compared for the different slice thicknesses using a pooled analysis of both reviewers. Significant CAD was defined as >50% diameter narrowing on quantitative CCA. Image noise (standard deviation of CT numbers) was measured in all scans. Inter-observer variability was assessed with kappa.
Results: Significant CAD was present in 8% of 304 available segments. Median total Agatston calcium score was 181.8 (interquartile range 34.9–815.6). Sensitivity at 0.67 mm, 0.9 mm, and 1.4 mm slice thickness was 70% (95% confidence interval 57–83%), 74% (62–86%), and 70% (57–83%), respectively. Specificity was 85% (82–88%), 84% (81–87%), and 84% (81–87%), respectively. The positive predictive value was 30 (21–38%), 29 (21–37%), and 28 (20–36%), respectively. The negative predictive value was 97% (95–98%), 97% (96–99%), and 97% (96–99%), respectively. Kappa for inter-observer agreement was 0.56, 0.58, and 0.59. Noise decreased from 32.9 HU at 0.67 mm, to 23.2 HU at 1.4 mm (P<0.001).
Conclusion: Diagnostic performance of CTCA in angina patients with a positive calcium score was not markedly affected by modest variations in reconstruction slice thickness.
Acknowledgments
This research was supported by an unrestricted grant from ZonMW. Additional funding was obtained from the Van Ruijven and Bekalis Foundation (P.A.D.).
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.