Optimal boundary detection method and window settings for coronary atherosclerotic plaque volume analysis in coronary computed tomography angiography: comparison with intravascular ultrasound

Objective: To evaluate optimal methodology for quantitative plaque volume analysis by coronary CT angiography (QCT). Methods: Fifty-one coronary artery segments were evaluated and contour measurements based on two different methods [(1) no gap, or (2) fixed 0.3-mm gap between inner and outer boundary] were compared with intravascular ultrasound (IVUS). In addition, three different window width (WW) and level (WL) settings [fixed (740/220) Hounsfield unit (HU), adjusted (155 % and 65 % of mean luminal intensity of the segment, and aorta adjusted (155 % and 65 % of mean luminal intensity of central aorta)] were used for semiautomated plaque volume analysis. Results: For boundary detection, the no gap method led to underestimation compared with IVUS (105.4 ± 82.3 vs. 136.1 ± 72.8 mm³, p < 0.001), while fixed 0.3-mm gap showed no difference between IVUS and QCT (136.1 ± 72.8 vs. 139.8 ± 93.9 mm³, p = 0.50). Comparison of the three different window settings demonstrated that the aorta adjusted setting underestimated (120.5 ± 74.3 vs. 136.1 ± 72.8 mm³, p = 0.003), while fixed setting showed the least mean difference compared with IVUS (3.8 ± 39.8 mm³, p = 0.50). Conclusion: For plaque volumetric assessment, optimal results were obtained with fixed 0.3-mm gap with fixed HU setting (740/220). Key Points: • Quantitative plaque volume analysis by coronary CT angiography has recently emerged. • Different boundary detection methods and window width and level settings were evaluated. • Fixed 0.3-mm gap with fixed HU setting (740/220) afforded optimal results.