Coronary Plaque Quantification by Voxel Analysis: Dual-Source MDCT Angiography Versus Intravascular Sonography

OBJECTIVE. The purpose of this study was to evaluate a voxel-based analytic technique for quantification of noncalcified coronary artery plaque with intravascular sonography as a standard of reference. SUBJECTS AND METHODS. Intravascular sonography and dual-source MDCT angiography prospectively performed on 12 patients resulted in identification of 20 segments containing noncalcified plaque. Four of these segments were used to establish reference measurements of 0.6-mm proximal wall thickness with a 0-HU cutoff between the epicardial fat and outer wall and an individually adjusted threshold for the interface between the wall and lumen. With these data, consecutive circular layers of the outer wall were subtracted from a 3D volume to determine the plaque plus medial layer and the actual plaque volume in the other 16 segments. Accuracy of the voxel technique was assessed by comparing the results with intravascular sonographic findings. RESULTS. Both the total plaque burden (plaque plus medial layer) and the actual plaque volume had good concordance with intravascular sonographic findings (49.6 +/- 20 mm(3) vs 56.7 +/- 23.6 mm(3), p = 0.076; 26.5 +/- 14.8 mm(3) vs 30.9 +/- 15.3 mm(3), p = 0.09). Corresponding correlation coefficients were r = 0.76 and r = 0.79. The method had good reproducibility, the an intraclass correlation coefficients being 0.93 for total plaque burden and 0.90 for actual plaque volume. CONCLUSION. Voxel analysis can be used for accurate and reproducible quantification not only of plaque burden but also of actual plaque volume.