title: In vivo MRI-based simulation of fatigue process: a possible trigger for human carotid atherosclerotic plaque rupture.
abstract: BACKGROUND
  Atherosclerotic plaque is subjected to a repetitive deformation due to arterial pulsatility during each cardiac cycle and damage may be accumulated over a time period causing fibrous cap (FC) fatigue, which may ultimately lead to rupture. In this study, we investigate the fatigue process in human carotid plaques using in vivo carotid magnetic resonance (MR) imaging.
  
  
  METHODS
  Twenty seven patients with atherosclerotic carotid artery disease were included in this study. Multi-sequence, high-resolution MR imaging was performed to depict the plaque structure. Twenty patients were found with ruptured FC or ulceration and 7 without. Modified Paris law was used to govern crack propagation and the propagation direction was perpendicular to the maximum principal stress at the element node located at the vulnerable site.
  
  
  RESULTS
  The predicted crack initiations from 20 patients with FC defect all matched with the locations of the in vivo observed FC defect. Crack length increased rapidly with numerical steps. The natural logarithm of fatigue life decreased linearly with the local FC thickness (R(2) = 0.67). Plaques (n=7) without FC defect had a longer fatigue life compared with those with FC defect (p = 0.03).
  
  
  CONCLUSIONS
  Fatigue process seems to explain the development of cracks in FC, which ultimately lead to plaque rupture.
authors.affiliation: University Department of Radiology, University of Cambridge, Level 5, Box 218, Hills Road, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Huang
authors.forename: Zhongzhao
authors.initials: Z
authors.lastname: Teng
authors.forename: Umar
authors.initials: U
authors.lastname: Sadat
authors.forename: Jing
authors.initials: J
authors.lastname: He
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Graves
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Gillard
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000473:pathology; D001696:Biomechanical Phenomena; D002340:Carotid Artery Diseases / Q000150:complications / Q000473:pathology; D003198:Computer Simulation; D005260:Female; D005355:Fibrosis / Q000209:etiology / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012421:Rupture / Q000209:etiology / Q000473:pathology*; D013312:Stress, Physiological