Computational Modeling and Simulation Examples in Bioengineering. Группа авторов
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СКАЧАТЬ [81] suggested that the wall thickness as a constant value is not accurate and described a novel method that incorporated the regionally varying wall thickness, especially in the area of rupture.

      Most aneurysms have ILT within their lumen. Stenbaek et al. [82] described that the development of ILT may be a better predictor than the maximum diameter of the AAA as a rupture risk parameter. Li et al. [83] calculated that the non‐ILT models had higher stress development than the ILT models. Di Martino and Vorp [84] found that ILT might protect the AAA wall from the pressure applied by blood flow. O'Leary et al. [85] performed mechanical tests on 356 samples and classified them into 3 morphologies, type 1 which was a multilayered ILT which strength and stiffness decreased gradually, type 2 which strength decreased abruptly, and a single‐layered ILT with lower strength and stiffness compared with the other two types. Tong et al. [86] carried out biomechanical behavioral studies on 90 AAA samples (78 men and 12 women). They found that the female ILT luminal layer showed a lower stiffness in the longitudinal direction than male and, consequently, the thrombi may have different wall weakening effects in males and females. Speelman et al. [87–89] also showed that AAA wall stress is closely related to the AAA diameter. Namely, they investigated whether wall stress can be used to predict stable and progressive AAAs as well as the effect of ILT on wall stress. The study was conducted on the finite element models of 30 patients with wall stresses computed with and without ILT for stable and progressive AAAs. The results showed that ILT reduced AAA wall stress, progressive AAA growth was not related to the diameter but AAA volume and relative ILT volume, and that higher wall stress was related to AAA growth only when ILT was not included in the simulations.

      By using an inverse optimization method, Zeinali and Baek [103] created a computational framework toward patient‐specific AAA modeling. Namely, using a 3D geometry from medical images, they identified initial material parameters for healthy aorta to satisfy homeostatic condition and then created different computational shapes and considered multiple spatiotemporal forms of elastin degradation and stress‐mediated collagen turnover. The results exhibited the importance of the role of elastin damage extent, geometric complexity of an enlarged AAA, and sensitivity of stress‐mediated collagen turnover on the wall stress distribution and the rate of expansion. Also, the study showed that the distributions of stress and local expansion initially correspond to the extent of elastin damage, but change because of stress‐mediated tissue growth and remodeling dependent on the aneurysm shape. The specificity of their study lies in the fact that the authors did not use AAA patient‐specific model, but medical images of a healthy subject. On the other hand, they suggest that in spite of the model used for the present study, their computational framework could be used in a patient‐specific modeling to predict AAA shape and mechanical properties if improved in the domain of boundary conditions, description of aortic tissue, growth and remodeling, and the development of inverse scheme using AAA patients' longitudinal images.

      Meaningful СКАЧАТЬ