Simple geometric characteristics fail to reliably predict abdominal aortic aneurysm wall stresses
Simple geometric characteristics fail to reliably predict abdominal aortic aneurysm wall stresses
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DOI：
10.1067/mva.2001.114815
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发表时间：
2001-08-01
影响因子：
4.3
通讯作者：
Mower, WR
中科院分区：
文献类型：
--
作者：
Hua, J;Mower, WR
目的：腹主动脉瘤(AAA)患者的治疗通常基于破裂的可能性。目前的破裂评估又是基于总体人口的统计数据，无法为单个AAA提供准确的风险估计。如果能够根据简单的几何特征或对称薄壳分析的结果可靠地确定单个AAA的破裂潜力，则可以实现显著的效益。本研究旨在确定是否有可能使用这些简单的测量方法来估计壁应力。方法：采用线性有限元分析方法，在假设残余应力为零的情况下，估计了一系列均匀、各向同性、三维AAA模型在静载作用下的von Mise应力分布。将每个模型的峰值应力大小与下列特征一起列成表格：动脉瘤体积；最大直径；最大半径；最大壁扩张；长宽比(最大前后径与横径之比)；局部曲率半径(纵向和周向)；以及最大对称薄壳应力估计(基于子午线轮廓)。结果：各模型的峰值应力范围为1.79×10(6)dyne/cm(2)~15.1×10(6)dyne/cm(2)。周向和纵向曲率半径往往能够预测高应力的位置，但不能预测峰值应力的大小。高宽比与最大壁应力的相关性最强(r=0.88，95%CI，0.68~0.96)，其他指标相关性更差。对称薄壳分析能够准确地预测轴对称模型中的应力，但不能预测非对称模型中应力峰值的位置和大小。结论：简单的几何准则和对称薄壳分析不能预测AAA应力。未来估计单个AAA的壁应力和评估破裂风险的尝试可能需要详细的三维建模。
Purpose: The treatment of patients with abdominal aortic aneurysms (AAAs) is typically based on the potential for rupture. Current rupture assessments are in turn based on statistics from aggregate populations and are incapable of providing precise risk estimates for individual AAAs. Significant benefit could be realized if rupture potential for individual AAAs could be reliably determined on the basis of simple geometric characteristics or the results of symmetric thin-shell analysis. This study seeks to determine whether it is possible to estimate wall stresses by use of these simple measures.Methods: Linear finite element analysis was used to estimate the distribution of von Mises stresses in a series of homogeneous, isotropic, three-dimensional AAA models subject to static loading and assumed to have zero residual stresses. The magnitude of the peak stress was tabulated for each model along with the following characteristics: aneurysm volume; maximum diameter; maximum radius; maximal wall distention; aspect ratio (ratio of greatest anteroposterior diameter to transverse diameter); local radii of curvature (in both longitudinal and circumferential directions); and maximum symmetric thin-shell stress estimates (on the basis of the meridional contour). The relationship between peak stress and each of the characteristics was assessed by use of Spearman rank correlation coefficients, with values less than 0.95 interpreted as signifying unreliable associations.Results: Peak stresses in the individual models ranged from 1.79 x 10(6) dyne/cm(2) to 15.1 x 10(6) dyne/cm(2). The circumferential and longitudinal radii of curvature were frequently able to predict the locations of high stress, but were unreliable in predicting the magnitude of peak stress. The aspect ratio showed the strongest correlation with peak wall stress (r = 0.88, 95% CI, 0.68-0.96), whereas the other characteristics showed even less correlation. Symmetric thin shell analysis accurately predicted stresses in axially symmetric models, but it was incapable of predicting either the location or magnitude of peak stress in asymmetric models.Conclusions: Simple geometric criteria and symmetric thin shell analyses are unreliable in predicting AAA stresses. Future attempts to estimate wall stress and assess risk of rupture for individual AAAs may require detailed three-dimensional modeling.