Three-dimensional ultrasound for carotid vessel wall volume measurement

Objectives: The intima-media thickness (IMT) of the carotid artery can now be detected on a three-dimensional (3D) plane. The 3D vessel wall volume (VWV) more accurately represents vascular conditions. Through 3D ultrasound, we established a standardized method for carotid VWV measurement. Materials and Methods: A total of thirty patients without stroke or cardiovascular disease who received carotid duplex sonography were retrospectively reviewed. Gray-scale 3D images from the distal common carotid artery (CCA) to internal carotid artery on both sides were acquired using a single-sweep 3D transducer and analyzed offline by using the vascular plaque quantification function of the Philips QLAB software. Then, the 3D IMT(QLAB intima-media thickness [QIMT]), total plaque volume (TPV), and VWV were measured by a neurologist and a technician, and the interobserver variability was assessed. Results: The mean two-dimensional (2D) carotid IMT was 0.65 +/- 0.12 mm. The mean QIMT, TPV, and VWV measured by observer 1 were 0.68 +/- 0.18 mm, 26 +/- 12 mm3, and 94 +/- 10 mm3, respectively. The Bland-Altman plot of the mean differences between the QIMT, TPV, and VWV values measured by observers 1 and 2 showed that those of observer 2 were within two standard deviations of those of observer 1. Intraclass correlation coefficients (ICCs) indicated strong correlations in QIMT (ICC = 0.76), TPV (ICC = 0.85), and VWV (ICC = 0.90; P < 0.001) between observers 1 and 2. Both 2D IMT and 3D QIMT exhibited a positive linear correlation with age. Conclusion: This study established a standardized VWV measurement through 3D ultrasound. Reasonable interobserver differences were obtained within a 95% limit of agreement and high reliability (ICC = 0.90). The VWV 1 cm from the CCA bifurcation was quantified with a mean value of 94.2 mm3. Further studies on the 3D ultrasound quantification of carotid arteries are warranted.