Preliminaryin vivoatherosclerotic carotid plaque characterization using the accumulated axial strain and relative lateral shift strain indices

Abstract

In this paper, we explore two parameters or strain indices related to plaque deformation during the cardiac cycle, namely, the maximum accumulated axial strain in plaque and the relative lateral shifts between plaque and vessel wall under in vivo clinical ultrasound imaging conditions for possible identification of vulnerable plaque. These strain indices enable differentiation between calcified and lipidic plaque tissue utilizing a new perspective based on the stiffness and mobility of the plaque. In addition, they also provide the ability to distinguish between softer plaques that undergo large deformations during the cardiac cycle when compared to stiffer plaque tissue. Soft plaques that undergo large deformations over the cardiac cycle are more prone to rupture and to release microemboli into the cerebral bloodstream. The ability to identify vulnerable plaque, prone to rupture, would significantly enhance the clinical utility of this method for screening patients. We present preliminary in vivo results obtained from ultrasound radio frequency data collected over 16 atherosclerotic plaque patients before these patients undergo a carotid endarterectomy procedure. Our preliminary in vivo results indicate that the maximum accumulated axial strain over a cardiac cycle and the maximum relative lateral shift or displacement of the plaque are useful strain indices that provide differentiation between soft and calcified plaques.

Validation of Noninvasive In Vivo Compound Ultrasound Strain Imaging Using Histologic Plaque Vulnerability Features

“…3,[7][8][9][10][11][12][13] Background and Purpose-Carotid plaque rupture is a major cause of stroke. Key issue for risk stratification is early identification of rupture-prone plaques.…”

“…Lately, noninvasive variants were introduced for carotid arteries, mostly for longitudinal imaging planes. [9][10][11][12] However, imaging in longitudinal planes only allows visualization of the anterior and posterior wall. Because plaque can be present all over the circumference, we developed a technique for accurate estimation of radial strains in transverse imaging planes by using radiofrequency ultrasound data acquired at 3 insonification angles.…”

Ultrasound elastography using multiple images

“…the Lagrangian particle tracking (e.g. for cardiac strain imaging over the cardiac cycle (Shi et al, 2008;Ma and Varghese, 2012)), and (2) strain images are averaged to reduce noise. In Lagrangian particle tracking, one should note that the location of a particle keeps changing in the image sequence, and therefore appropriate displacements must be accumulated.…”

“…This assumption breaks for vascular strain imaging where the two vessel walls can move in opposite directions (Shi and Varghese, 2007;Shi et al, 2008). This issue also has been addressed in model-based elasticity reconstruction problems by assigning soft and hard constraints (Le Floc'h et al, 2009;Richards and Doyley, 2011).…”

Estimation of the viscoelastic properties of vessel walls using a computational model and Doppler ultrasound

“…Other authors (Shi et al, 2008;Danilouchkine et al, 2009) proposed the use of high resolution intravascular ultrasound (IVUS) imaging. Preliminary results in the plaque characterization were also obtained using Acoustic Radiation Force Imaging (Dahl et al, 2009).…”