Quantification of Atherosclerotic Plaque Elasticity Using Ultrasonic Texture Matching

The composition of an atherosclerotic plaque is a major determinant of its vulnerability, i.e. proneness to rupture. This paper proposes an ultrasonic texture matching method, which is shown to reflect the distribution of elastic modulus and is a potential method for quantitatively analyzing different plaque components based on B-mode cine-loops. We performed an in vitro study, employing plaque phantoms fabricated using polyvinyl alcohol. Firstly, the phantoms with two components (soft tissue: 60.9 ± 6.8 kPa; surrounding tissue: 248.8 ± 12.1 kPa) were fabricated. Soft tissue occupied 10%, 40% and 64% of the total plaque volume. Further, three tissue components (soft tissue: 60.9 ± 6.8 kPa; hard tissue: 248.8 ± 12.1 kPa; surrounding tissue: 310.3 ± 14.1 kPa) were made. Soft and hard tissues occupied 32% of total plaque volume, respectively. For our in vivo study, six mice with ApoE knockout and three New Zealand white rabbits with abdominal aortic balloon injury were evaluated. Ultrasound cine-loop data of plaques were collected to calculate elastic modulus, then the plaque tissues were removed for further histology examination. The cine-loop data in vitro study and in vivo study were acquired by an ultrasound micro-imaging system (VisualSonics Vevo2100). In the phantom experiment, the mean elastic moduli of two component phantoms were 60.4 ± 7.6 kPa (soft tissue) and 198.5 ± 12.5 kPa (surrounding tissue), respectively. Similarly, the mean elastic moduli of three component phantoms exhibited 90.2 ± 6.2 kPa (soft tissue), 184.3 ± 11.6 kPa (hard tissue) and 381.6 ± 3.8 kPa (surrounding tissue), respectively. In animal experiments, the percentage of lipid tissue and calcification regions was also quantified in mice and in rabbit experiment with the histological results. This suggests that the texture matching method may be a potential method to identify lipid component of plaque and to predict the vulnerability of atherosclerosis plaques noninvasively.