Mines Saint-Étienne, CIS-EMSE, 42023, Saint-Étienne, France.
INSERM, U1059, SAINBIOSE, 42023, Saint-Étienne, France.
Biomech Model Mechanobiol. 2019 Feb;18(1):137-153. doi: 10.1007/s10237-018-1073-0. Epub 2018 Aug 25.
Aortic dissection is the most common catastrophe of the thoracic aorta, with a very high rate of mortality. Type A dissection is often associated with an ascending thoracic aortic aneurysm (ATAA). However, it is widely acknowledged that the risk of type A dissection cannot be reliably predicted simply by measuring the ATAA diameter and there is a pressing need for more reliable risk predictors. It was previously shown that there is a significant correlation between a rupture criterion based on the ultimate stretch of the ATAA and the local extensional stiffness of the aorta. Therefore, reconstructing regional variations of the extensional stiffness across the aorta appears highly important. In this paper, we present a novel noninvasive inverse method to identify the patient-specific local extensional stiffness of aortic walls based on preoperative gated CT scans. Using these scans, a structural mesh is defined across the aorta with a set of nodes attached to the same material points at different time steps throughout the cardiac cycle. For each node, time variations of the position are analyzed using Fourier series, permitting the reconstruction of the local strain distribution (fundamental term). Relating these strains to tensions with the extensional stiffness, and writing the local equilibrium satisfied by the tensions, the local extensional stiffness is finally derived at every position. The methodology is applied onto the ascending and descending aorta of three patients. Interestingly, the regional distribution of identified stiffness properties appears heterogeneous across the ATAA. Averagely, the identified stiffness is also compared with values obtained using other nonlocal methodologies. The results support the possible noninvasive prediction of stretch-based rupture criteria in clinical practice using local stiffness reconstruction.
主动脉夹层是胸主动脉最常见的灾难性疾病，死亡率非常高。A型夹层通常与升主动脉瘤（ATAA）有关。然而，人们普遍认为，仅凭测量 ATAA 直径无法可靠预测 A 型夹层的风险，因此迫切需要更可靠的风险预测指标。先前的研究表明，基于 ATAA 极限拉伸的破裂标准与主动脉的局部拉伸刚度之间存在显著相关性。因此，重建主动脉跨区的拉伸刚度变化显得非常重要。在本文中，我们提出了一种新颖的无创逆方法，该方法基于术前门控 CT 扫描来识别患者特定的主动脉壁局部拉伸刚度。使用这些扫描，在整个心动周期中，在主动脉上定义一个结构网格，网格上有一组节点附着在同一材料点上。对于每个节点，使用傅里叶级数分析位置的时间变化，从而重建局部应变分布（基本项）。将这些应变与拉伸刚度相关联，并写出张力满足的局部平衡，最终可以在每个位置推导出局部拉伸刚度。该方法应用于三名患者的升主动脉和降主动脉。有趣的是，在所研究的 ATAA 中，确定的刚度特性的区域分布呈现出不均匀性。平均而言，还将识别出的刚度与使用其他非局部方法获得的值进行了比较。结果支持使用局部刚度重建在临床实践中对基于拉伸的破裂标准进行无创预测。
