To noninvasively assess the risk of aneurysm rupture and dissection, an accurate material failure metric of the aortic wall is crucial. Previous studies used deterministic or isotropic failure metrics for the aortic wall. However, experimental studies have shown that aortic wall tensile strengths in circumferential and axial directions are significantly different (i.e., anisotropic) and vary greatly among patients. In this study, we developed a new probabilistic and anisotropic material failure metric for rupture risk assessment of ascending thoracic aortic aneurysm (ATAA). We performed uniaxial tensile failure tests using aortic tissue samples of 84 ATAA patients, from which a joint probability distribution of the anisotropic wall strengths was obtained. Subsequently, we derived an anisotropic failure probability (FP) metric based on the Tsai-Hill (TH) failure criterion. The novel FP metric incorporates uncertainty and anisotropy of failure properties. To compare the FP metric with traditional deterministic and isotropic metrics, we numerically estimated “baseline” risks of additional 41 ATAA patients using matching CT images and tissue testing data. We presented different risk assessment methods (e.g., with and without patient-specific hyperelastic properties) and compared them using receiver operating characteristic (ROC) curves. The results demonstrated that: (1) the probabilistic FP metric outperforms the deterministic TH metric and the isotropic maximum principal stress; (2) patient-specific hyperelastic properties can help to improve the performance of probabilistic FP metric in ATAA risk assessment. The proposed probabilistic modeling framework may be adopted for other types of materials.

为了无创评估动脉瘤破裂和夹层的风险，主动脉壁的准确材料失效指标至关重要。以前的研究使用主动脉壁的确定性或各向同性失败指标。然而，实验研究表明，主动脉壁在周向和轴向上的抗张强度存在显着差异（即各向异性），并且患者之间差异很大。在这项研究中，我们开发了一种新的概率和各向异性材料失效指标，用于评估升胸主动脉瘤 (ATAA) 的破裂风险。我们使用 84 名 ATAA 患者的主动脉组织样本进行了单轴拉伸失效测试，从中获得了各向异性壁强度的联合概率分布。随后，我们基于 Tsai-Hill (TH) 故障准则推导出各向异性故障概率 (FP) 度量。新的 FP 度量结合了故障属性的不确定性和各向异性。为了将 FP 度量与传统的确定性和各向同性度量进行比较，我们使用匹配的 CT 图像和组织测试数据对另外 41 名 ATAA 患者的“基线”风险进行了数值估计。我们提出了不同的风险评估方法（例如，有和没有患者特定的超弹性特性），并使用受试者工作特征（ROC）曲线进行比较。结果表明：（1）概率FP度量优于确定性TH度量和各向同性最大主应力；(2) 患者特定的超弹性特性有助于提高概率 FP 度量在 ATAA 风险评估中的性能。