Abstract
Fatal cerebrovascular events are often caused by rupture of atherosclerotic plaques. However, rupture-prone plaques are often distinguished by their internal composition rather than degree of luminal narrowing, and conventional imaging techniques might thus fail to detect such culprit lesions. In this feasibility study, we investigate the potential of ultrasound shear wave elastography (SWE) to detect vulnerable carotid plaques, evaluating group velocity and frequency-dependent phase velocities as novel biomarkers for plaque vulnerability. In total, 27 carotid plaques from 20 patients were scanned by ultrasound SWE and magnetic resonance imaging (MRI). SWE output was quantified as group velocity and frequency-dependent phase velocities, respectively, with results correlated to intraplaque constituents identified by MRI. Overall, vulnerable lesions graded as American Heart Association (AHA) type VI showed significantly higher group and phase velocity compared to any other AHA type. A selection of correlations with intraplaque components could also be identified with group and phase velocity (lipid-rich necrotic core content, fibrous cap structure, intraplaque hemorrhage), complementing the clinical lesion classification. In conclusion, we demonstrate the ability to detect vulnerable carotid plaques using combined SWE, with group velocity and frequency-dependent phase velocity providing potentially complementary information on plaque characteristics. With such, the method represents a promising non-invasive approach for refined atherosclerotic risk prediction.
Highlights
Atherosclerotic disease is recognized as a diffuse systemic vascular process, and rupture and erosion of carotid atherosclerotic plaques is the number one cause of cerebrovascular mortality in the world[1]
The results show that identification of vulnerable lesions can be achieved using shear wave elastography (SWE), where American Heart Association (AHA) type VI plaques showed significantly higher group velocity, with similar trends indicated for high-frequency phase velocity
A set of novel SWE-based biomarkers have been identified, with group velocity and phase velocity correlating with plaque lipid-rich necrotic core (LRNC) content, fibrous cap/necrotic core volume ratio, and intraplaque hemorrhage (IPH) volume; all entities associated with status of plaque stability
Summary
Atherosclerotic disease is recognized as a diffuse systemic vascular process, and rupture and erosion of carotid atherosclerotic plaques is the number one cause of cerebrovascular mortality in the world[1]. The spatial confinements and complex composition of atherosclerotic plaque affects accuracy[18,19], and in-vitro studies have shown that combined spatiotemporal and frequency-dependent shear wave analysis might be required for accurate plaque differentiability[18]. Such analysis has yet to be evaluated in-vivo. The aim of this study was to, for the first time, apply combined spatiotemporal and frequency-dependent ultrasound shear wave elastography (SWE) to non-invasively assess atherosclerotic plaque characteristics in-vivo. Group velocity and phase velocity SWE were assessed on a carotid plaque cohort, evaluating and validating output against reference MRI
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