title: The influence of constitutive law choice used to characterise atherosclerotic tissue material properties on computing stress values in human carotid plaques.
abstract: Calculating high stress concentration within carotid atherosclerotic plaques has been shown to be complementary to anatomical features in assessing vulnerability. Reliability of stress calculation may depend on the constitutive laws/strain energy density functions (SEDFs) used to characterize tissue material properties. Different SEDFs, including neo-Hookean, one-/two-term Ogden, Yeoh, 5-parameter Mooney-Rivlin, Demiray and modified Mooney-Rivlin, have been used to describe atherosclerotic tissue behavior. However, the capacity of SEDFs to fit experimental data and the difference in the stress calculation remains unexplored. In this study, seven SEDFs were used to fit the stress-stretch data points of media, fibrous cap, lipid and intraplaque hemorrhage/thrombus obtained from 21 human carotid plaques. Semi-analytic solution, 2D structure-only and 3D fully coupled fluid-structure interaction (FSI) analyses were used to quantify stress using different SEDFs and the related material stability examined. Results show that, except for neo-Hookean, all other six SEDFs fitted the experimental points well, with vessel stress distribution in the circumferential and radial directions being similar. 2D structural-only analysis was successful for all seven SEDFs, but 3D FSI were only possible with neo-Hookean, Demiray and modified Mooney-Rivlin models. Stresses calculated using Demiray and modified Mooney-Rivlin models were nearly identical. Further analyses indicated that the energy contours of one-/two-term Ogden and 5-parameter Mooney-Rivlin models were not strictly convex and the material stability indictors under homogeneous deformations were not always positive. In conclusion, considering the capacity in characterizing material properties and stabilities, Demiray and modified Mooney-Rivlin SEDF appear practical choices for mechanical analyses to predict the critical mechanical conditions within carotid atherosclerotic plaques.
authors.affiliation: Department of Radiology, University of Cambridge, UK; Department of Engineering, University of Cambridge, UK. Electronic address: zt215@cam.ac.uk.
authors.forename: Zhongzhao
authors.initials: Z
authors.lastname: Teng
authors.affiliation: Department of Radiology, University of Cambridge, UK.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Department of Vascular Surgery, Changhai Hospital, Shanghai, China.
authors.forename: Jiaxuan
authors.initials: J
authors.lastname: Feng
authors.affiliation: Department of Vascular Surgery, Changhai Hospital, Shanghai, China.
authors.forename: Yongxue
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Division of Cardiovascular Medicine, University of Cambridge, UK.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Brown
authors.affiliation: Department of Radiology, University of Cambridge, UK.
authors.forename: Shuo
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Vascular Surgery, Changhai Hospital, Shanghai, China.
authors.forename: Qingsheng
authors.initials: Q
authors.lastname: Lu
authors.affiliation: Department of Radiology, University of Cambridge, UK.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Gillard
mesh_terms: D000465:Algorithms; D002340:Carotid Artery Diseases / Q000503:physiopathology*; D006470:Hemorrhage / Q000503:physiopathology; D006801:Humans; D008962:Models, Theoretical; D058226:Plaque, Atherosclerotic / Q000503:physiopathology*; D015203:Reproducibility of Results; D013314:Stress, Mechanical
keywords: Atherosclerosis; Material property; Material stability; Strain energy density function; Stress