Coronary CT angiography: Variability of CT scanners and readers in measurement of plaque volume

Purpose: To determine reader and computed tomography (CT) scan variability for measurement of coronary plaque volume. Materials and Methods: This HIPAA-compliant study followed Standards for Reporting of Diagnostic Accuracy guidelines. Baseline coronary CT angiography was performed in 40 prospectively enrolled subjects (mean age, 67 years 6 6 [standard deviation]) with asymptomatic hyperlipidemia by using a 320-detector row scanner (Aquilion One Vision; Toshiba, Otawara, Japan). Twenty of these subjects underwent coronary CT angiography repeated on a separate day with the same CT scanner (Toshiba, group 1); 20 subjects underwent repeat CT performed with a different CT scanner (Somatom Force; Siemens, Forchheim, Germany [group 2]). Intraclass correlation coefficients (ICCs) and Bland- Altman analysis were used to assess interreader, intrareader, and interstudy reproducibility. Results: Baseline and repeat coronary CT angiography scans were acquired within 19 days 6 6. Interreader and intrareader agreement rates were high for total, calcified, and noncalcified plaques for both CT scanners (all ICCs 0.96) without bias. Scanner variability was 618.4% (coefficient of variation) with same-vendor follow-up. However, scanner variability increased to 629.9% with different-vendor follow-up. The sample size to detect a 5% change in noncalcified plaque volume with 90% power and an a error of .05 was 286 subjects for same-CT scanner follow-up and 753 subjects with different-vendor follow-up. Conclusion: State-of-the-art coronary CT angiography with same-vendor follow-up has good scan-rescan reproducibility, suggesting a role of coronary CT angiography in monitoring coronary artery plaque response to therapy. Differences between coronary CT angiography vendors resulted in lower scanrescan reproducibility.