Ultrasound (US) phenotypes of carotid atherosclerosis include intima–media thickness (IMT), total plaque area (TPA), total plaque volume (TPV), and Doppler ultrasound-based measurements of stenosis. Doppler US is a well-established screening tool in the assessment of stenosis severity. However, Doppler flow-velocity-based measurements do not provide information on plaque morphology, plaque vulnerability, or composition. The measurement of IMT from B-mode US images is a widely used US phenotype of atherosclerosis and has been regarded as a surrogate measurement of atherosclerosis as it correlates with vascular outcomes. Although the measurement of IMT has been validated in many studies, it is clear that many distinct biological pathways and mechanisms may be reflected by the measurement. More recently, TPA and TPV have emerged as useful US phenotypes of carotid atherosclerosis that measure plaque burden in 2D and 3D, respectively. Total plaque area has been shown to be a stronger predictor of coronary events than IMT [Spence et al., Stroke 33:2916–2922, 2002; Johnsen et al., Stroke 38(11):2873–2880, 2007].
In order to overcome some limitations and accelerate the translation of 3D US measurements of carotid atherosclerosis to clinical research and clinical practice, semiautomated methods of measurement and measurements that are derived from biological components of carotid disease with readily distinguishable US boundaries (enabling multiple observers to be trained in shorter time periods and with decreased interobserver variability) are required. This has stimulated the development and validation of a new 3D US measurement of carotid atherosclerosis – vessel wall volume (VWV), which is a measurement of vessel wall thickness and plaque within the common carotid artery, the internal and external carotid branches. This measurement can be more easily semiautomated, and observers can be trained to measure VWV in shorter durations and with greater reliability.
Our objective is to demonstrate that 3D US is a viable technique for quantifying the progression and regression of carotid atherosclerosis.