Accurate quantification of atherosclerotic plaque volume by 3D vascular ultrasound using the volumetric linear array method

- Novel 3D vascular ultrasound method for atherosclerotic plaque volume quantification is validated.
- Real 3DVUS accurately quantifies atherosclerotic plaques regardless of plaque size.
- Measurements are more accurate for superficial arterial territories (<5 cm-depth).
- This technique is more accurate than previous 3D-like methods for plaque burden estimation.

IntroductionDirect quantification of atherosclerotic plaque volume by three-dimensional vascular ultrasound (3DVUS) is more reproducible than 2DUS-based three-dimensional (2D/3D) techniques that generate pseudo-3D volumes from summed 2D plaque areas; however, its accuracy has not been reported. We aimed to determine 3DVUS accuracy for plaque volume measurement with special emphasis on small plaques (a hallmark of early atherosclerosis).MethodsThe in vitro study consisted of nine phantoms of different volumes (small and medium-large) embedded at variable distances from the surface (superficial vs. >5 cm-depth) and comparison of 3DVUS data generated using a novel volumetric-linear array method with the real phantom volumes. The in vivo study was undertaken in a rabbit model of atherosclerosis in which 3DVUS and 2D/3D volume measurements were correlated against gold-standard histological measurements.ResultsIn the in vitro setting, there was a strong correlation between 3DVUS measures and real phantom volume both for small (3.0-64.5 mm3 size) and medium-large (91.1-965.5 mm3 size) phantoms embedded superficially, with intraclass correlation coefficients (ICC) of 0.99 and 0.98, respectively; conversely, when phantoms were placed at >5 cm, the correlation was only moderate (ICC = 0.67). In the in vivo setting there was strong correlation between 3DVUS-measured plaque volumes and the histological gold-standard (ICC = 0.99 [4.02-92.5 mm3 size]). Conversely, the correlation between 2D/3D values and the histological gold standard (sum of plaque areas) was weaker (ICC = 0.87 [49-520 mm2 size]), with large dispersion of the differences between measurements in Bland-Altman plots (mean error, 79.2 mm2).Conclusions3DVUS using the volumetric-linear array method accurately measures plaque volumes, including those of small plaques. Measurements are more accurate for superficial arterial territories than for deep territories.