On the computation of in vivo transmural mean stress of patient-specific aortic wall.
On the computation of in vivo transmural mean stress of patient-specific aortic wall.
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DOI：
10.1007/s10237-018-1089-5
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发表时间：
2019-04
影响因子：
3.5
通讯作者：
Sun W
中科院分区：
文献类型：
--
作者：
Liu M;Liang L;Liu H;Zhang M;Martin C;Sun W
众所周知，残余变形/应力会改变动脉的力学行为，例如压力-直径曲线。在使用厚壁模型的有限元模拟中，为了能够对主动脉壁应力进行个性化分析，已经开发出将实验得出的残余变形合并到活体加载几何中的方法。实体单元通常用来解释“弯曲状”的残余变形。然而，难以获得患者特定的残余变形和材料特性已成为这些厚壁模型的最大挑战之一。幸运的是，在薄壁模型中，静态确定性提供了一个吸引人的前景，允许在没有患者特定材料特性的情况下计算薄壁薄膜应力。通过施加极硬的材料特性作为惩罚处理，可以使用正向分析来计算薄膜应力，这被称为正向惩罚方法。然而，具有零弯曲刚度的薄壁薄膜单元与残余变形是不相容的，因此，它通常被认为是薄壁模型的限制。在本文中，通过比较薄壁模型和厚壁模型的预测应力，我们证明了两种模型的跨壁平均应力大致相同，并且可以很容易地从活体临床图像中获得，而不需要知道患者特定的材料特性和残余变形。采用正向惩罚方法可以大大简化患者特定平均应力的计算，这可能具有临床价值。
It is well known that residual deformations/stresses alter the mechanical behavior of arteries, e.g. the pressure-diameter curves. In an effort to enable personalized analysis of the aortic wall stress, approaches have been developed to incorporate experimentally-derived residual deformations into in vivo loaded geometries in finite element simulations using thick-walled models. Solid elements are typically used to account for “bending-like” residual deformations. Yet, the difficulty in obtaining patient-specific residual deformations and material properties has become one of the biggest challenges of these thick-walled models. In thin-walled models, fortunately, static determinacy offers an appealing prospect that allows for the calculation of the thin-walled membrane stress without patient-specific material properties. The membrane stress can be computed using forward analysis by enforcing an extremely stiff material property as penalty treatment, which is referred to as the forward penalty approach. However, thin-walled membrane elements, which have zero bending stiffness, are incompatible with the residual deformations, and therefore, it is often stated as a limitation of thin-walled models. In this paper, by comparing the predicted stresses from thin-walled models and thick-walled models, we demonstrate that the transmural mean stress is approximately the same for the two models and can be readily obtained from in vivo clinical images without knowing the patient-specific material properties and residual deformations. Computation of patient-specific mean stress can be greatly simplified by using the forward penalty approach, which may be clinically valuable.
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