Harald Brodoefel, MD, from the department of radiology at Beth Israel Deaconess Medical Center in Boston, and colleagues sought to evaluate a voxel-based analytic technique for quantification of noncalcified coronary artery plaque with intravascular sonography as a standard of reference.
The researchers prospectively performed intravascular sonography and dual-source CT angiography on 12 patients and identified 20 segments containing noncalcified plaque. Four of the 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, the investigators subtracted the consecutive circular layers of the outer wall from a 3D volume to determine the plaque plus medial layer and the actual plaque volume in the other 16 segments. They assessed the accuracy of the voxel technique by comparing the results with intravascular sonographic findings.
Both the total plaque burden (plaque plus medial layer) and the actual plaque volume had good concordance with intravascular sonographic findings (49.6 mm3 vs. 56.7 mm3; 26.5 mm3 vs. 30.9 mm3), according to the researchers.
Brodoefel and colleagues found that the method had good reproducibility, and the intra-class correlation coefficients being 0.93 for total plaque burden and 0.90 for actual plaque volume.
The authors concluded that their "results with voxel analysis technique suggest the potential for adequate and reproducible quantification of noncalcified atheroma in terms of both total plaque burden and volume of the actual plaque tissue. Whether quantification of actual plaque is advantageous in the assessment of serial plaque stabilization remains open to further investigation."