The sudden rupture of carotid artery plaques can trigger an ischemic stroke event and eventually lead to death. Unfortunately, the identification of unstable plaques continues to elude clinicians. The use of Acoustic Radiation Force (ARF) to non-invasively provide a relative measure of tissue stiffness has shown promise for differentiating softer, lipid filled plaque regions believed to be more vulnerable than stiffer, calcified plaque regions¹.

A Finite Element Method (FEM) model to simulate the resultant displacements and associated stresses generated by ARF in vivo was implemented to demonstrate the feasibility of this ultrasound-based technique to characterize rupture prone plaques. A parametric analysis was performed by varying tissue and acoustic beam characteristics for different vasculature and plaque component geometries, based on published images of in vivo carotid artery plaques obtained using MRI by Li et al.²

ARF induced displacements within the modelled artery were higher in the lipid (0 to 2 μm) compared to the surrounding vessel and fibrous cap (0 to 1 μm) and are consistent with in vivo measurements. The maximum equivalent stress increased with an increase in the fibrous cap stiffness and for the geometry shown in Figure 1 was <406 Pa for all parametric cases. A more detailed analysis of the FEM model parameters and results for other geometries will be presented along with in vivo ARFI images.

Figure 1:

Depicting the increased displacements in the lipid pool and maximum equivalent stress concentration in the fibrous cap.