Li Zhi-Yong, Howarth Simon, Trivedi Rikin A, U-King-Im Jean M, Graves Martin J, Brown Andrew, Wang Liqun, Gillard Jonathan H
Department of Radiology, Addenbrooke's Hospital and University of Cambridge, Cambridge, CB2 2QQ, United Kingdom.
J Biomech. 2006;39(14):2611-22. doi: 10.1016/j.jbiomech.2005.08.022. Epub 2005 Oct 26.
Atheromatous carotid plaque rupture is responsible for the majority of ischaemic strokes in the developed world. Plaque rupture has been associated with plaque morphology, plaque components' properties, inflammation and local stress concentration. High resolution multi-spectral magnetic resonance imaging (MRI) has allowed the plaque components to be visualized in vivo. This study combined the recent advances in finite element analysis (FEA) and MRI, and performed stress analysis of five vulnerable carotid plaques based on the geometry derived from in vivo MRI. Image segmentation was based on multi-spectral MRI and co-registered with histology for plaque characterization. Plaque fibrous cap, lipid pool and vessel wall were modelled as isotropic, incompressible hyperelastic materials undergoing large deformation under pulse pressure loading. High stress concentrations were predicted at the shoulders and the thinnest fibrous cap regions of the plaque, and the mean maximal stresses were found to be higher in the ruptured plaques (683.3 kPa) than those in the unruptured plaques (226.9 kPa). The effect of the relative stiffness of fibrous cap to lipid pool on the stress within the cap itself was studied. It was shown that larger relative stiffness of fibrous cap to lipid pool resulted in higher stress within the cap. Thus, it is likely that high stress concentrations in vulnerable plaque may cause plaque rupture and lead to acute ischaemic sequelae. A combination of in vivo high resolution MRI and FEA could potentially act as a useful tool to assess plaque vulnerability and risk stratify patients with carotid atheroma.
在发达国家，动脉粥样硬化性颈动脉斑块破裂是大多数缺血性中风的病因。斑块破裂与斑块形态、斑块成分特性、炎症及局部应力集中有关。高分辨率多光谱磁共振成像（MRI）已能够在体内观察斑块成分。本研究结合了有限元分析（FEA）和MRI的最新进展，基于体内MRI获取的几何形状对五个易损颈动脉斑块进行了应力分析。图像分割基于多光谱MRI，并与组织学进行配准以表征斑块。将斑块纤维帽、脂质池和血管壁建模为在脉冲压力载荷下发生大变形的各向同性、不可压缩超弹性材料。预测在斑块肩部和最薄纤维帽区域会出现高应力集中，且发现破裂斑块中的平均最大应力（683.3 kPa）高于未破裂斑块（226.9 kPa）。研究了纤维帽与脂质池的相对刚度对纤维帽内部应力的影响。结果表明，纤维帽与脂质池的相对刚度越大，纤维帽内的应力越高。因此，易损斑块中的高应力集中很可能导致斑块破裂并引发急性缺血性后遗症。体内高分辨率MRI和FEA相结合可能成为评估斑块易损性及对颈动脉粥样硬化患者进行风险分层的有用工具。
