Arterial stiffness identification of the human carotid artery using the stress–strain relationship in vivo

Abstract

Arterial stiffness is well accepted as a reliable indicator of arterial disease. Increase in carotid arterial stiffness has been associated with carotid arterial disease, e.g., atherosclerotic plaque, thrombosis, stenosis, etc. Several methods for carotid arterial stiffness assessments have been proposed. In this study, in-vivo noninvasive assessment using applanation tonometry and an ultrasound-based motion estimation technique was applied in seven healthy volunteers (age 28 ± 3.6 years old) to determine pressure and wall displacement in the left common carotid artery (CCA), respectively. The carotid pressure was obtained using a calibration method by assuming that the mean and diastolic blood pressures remained constant throughout the arterial tree. The regional carotid arterial wall displacement was estimated using a 1D cross-correlation technique on the ultrasound radio frequency (RF) signals acquired at a frame rate of 505–1010 Hz. Young’s moduli were estimated under two different assumptions: (i) a linear elastic two-parallel spring model and (ii) a two-dimensional, nonlinear, hyperelastic model. The circumferential stress (σθ) and strain (εθ) relationship was then established in humans in vivo. A slope change in the circumferential stress-strain curve was observed and defined as a transition point. The Young’s moduli of the elastic lamellae (E1), elastin-collagen fibers (E2) and collagen fibers (E3) and the incremental Young’s moduli before (E0≤εθ<ε0T) and after the transition point (EεθT≤εθ) were determined from the first and second approach, respectively, to describe the contribution of the complex mechanical interaction of the different arterial wall constituents. The average E1, E2 and E3 from seven healthy volunteers were found to be equal to 0.15 ± 0.04, 0.89 ± 0.27 and 0.75 ± 0.29 MPa, respectively. The average E0≤εθ<εθTInt and EεθT≤εθInt of the intact wall (both the tunica adventitia and tunica media layers) were found to be equal to 0.16 ± 0.04 MPa and 0.90 ± 0.25 MPa, respectively. The average E0≤εθ<εθTAd and EεθT≤εθAd of the tunica adventitia were found to be equal to 0.18 ± 0.05 MPa and 0.84 ± 0.22 MPa, respectively. The average EεθT≤εθMe and EεθT≤εθMe of the tunica media were found to be equal to 0.19 ± 0.05 MPa and 0.90 ± 0.25 MPa, respectively. The stiffness of the carotid artery increased with strain during the systolic phase of cardiac cycle. In conclusion, the feasibility of measuring the regional stress-strain relationship and stiffness of the normal human carotid artery noninvasively was demonstrated in human in vivo.

Assessing the Stability of Aortic Aneurysms with Pulse Wave Imaging

“…This is because the wave arrival time can be tracked as long as the displacement contains an axial component, which will be the case as long as the probe is not completely parallel to the vessel. This feature of PWI has been confirmed in successful applications of the technique in humans with clinically available equipment (20,32,33). Hence, the metrics of aneurysm stability proposed in this study are also angle independent and robust to changes in the field of view, which are important features for clinical practice.…”

p66Shc Couples Mechanical Signals to RhoA through Focal Adhesion Kinase-Dependent Recruitment of p115-RhoGEF and GEF-H1

“…timated to have Young's moduli of 700 to 900 kPa in vivo (31,32). Endothelial cells plated on collagen-coated polyacrylamide hydrogels demonstrated progressive flattening and proliferation rates on matrix beds with Young's moduli of between 13.6 and 95.1 kPa in addition to essentially nondeformable plastic (Fig.…”

Frictional characteristics of clamp surfaces of aneurysm clips finished by laser processing

“…The silicone tubing was 3 mm in outer diameter and 0.5 mm in thickness. Young' s moduli of the arteries range in value from 1 to 9 MPa in the literature (Gao, et al, 2006), (Horiuchi, et al, 2012), (Hučko, 2010), (Khamdaeng, et al, 2012). The static Young' s modulus of the silicone tubing used was about 4 MPa and the hardness was 56 Shore A.…”