Multidirectional Estimation of Arterial Stiffness Using Vascular Guided Wave Imaging with Geometry Correction

Yuexin Guo; Yahua Wang; Enoch Jing-Han Chang; Wei-Ning Lee

doi:10.1016/j.ultrasmedbio.2017.12.009

Multidirectional Estimation of Arterial Stiffness Using Vascular Guided Wave Imaging with Geometry Correction

Ultrasound Med Biol. 2018 Apr;44(4):884-896. doi: 10.1016/j.ultrasmedbio.2017.12.009.

Authors

Yuexin Guo¹, Yahua Wang¹, Enoch Jing-Han Chang¹, Wei-Ning Lee²

Affiliations

¹ Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong.
² Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong; Medical Engineering Programme, The University of Hong Kong, Hong Kong. Electronic address: wnlee@eee.hku.hk.

PMID: 29402485
DOI: 10.1016/j.ultrasmedbio.2017.12.009

Abstract

We previously found that vascular guided wave imaging (VGWI) could non-invasively quantify transmural wall stiffness in both the longitudinal (r-z plane, 0°) and circumferential (r-θ plane, 90°) directions of soft hollow cylinders. Arterial stiffness estimation in multiple directions warrants further comprehensive characterization of arterial health, especially in the presence of asymmetric plaques, but is currently lacking. This study therefore investigated the multidirectional estimation of the arterial Young's modulus in a finite-element model, in vitro artery-mimicking phantoms and an excised porcine aorta. A longitudinal pre-stretch of 20% and/or lumen pressure (15 or 70 mm Hg) was additionally introduced to pre-condition the phantoms for emulating the intrinsic mechanical anisotropy of the real artery. The guided wave propagation was approximated by a zero-order antisymmetric Lamb wave model. Shape factor, which was defined as the ratio of inner radius to thickness, was calculated over the entire segment of each planar cross section of the hollow cylindrical structure at a full rotation (0°-360° at 10° increments) about the radial axis. The view-dependent geometry of the cross segment was found to affect the guided wave propagation, causing Young's modulus overestimation in four angular intervals along the propagation pathway, all of which corresponded to wall regions with low shape factors (<1.5). As validated by mechanical tensile testing, the results indicate not only that excluding the propagation pathway with low shape factors could correct the overestimation of Young's modulus, but also that VGWI could portray the anisotropy of hollow cylindrical structures and the porcine aorta based on the derived fractional anisotropy values from multidirectional modulus estimates. This study may serve as an important step toward 3-D assessment of the mechanical properties of the artery.

Keywords: Anisotropy; Artery; Dispersion; Guided wave; Phase velocity; Shear modulus; Ultrasound.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Elasticity Imaging Techniques / methods*
Image Interpretation, Computer-Assisted / methods*
Image Processing, Computer-Assisted / methods*
Models, Animal
Phantoms, Imaging*
Swine
Vascular Stiffness*