Cardiovascular Biomechanics Group, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, the Netherlands.
Cardiovascular Biomechanics Group, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, the Netherlands; Department of Surgery, Catharina Hospital Eindhoven, P.O. Box 1350, 5602 ZA Eindhoven, the Netherlands.
J Biomech. 2019 Mar 6;85:126-133. doi: 10.1016/j.jbiomech.2019.01.024. Epub 2019 Jan 19.
In this study the influence of surrounding tissues including the presence of the spine on wall stress analysis and mechanical characterization of abdominal aortic aneurysms using ultrasound imaging has been investigated.
Geometries of 7 AAA patients and 11 healthy volunteers were acquired using 3-D ultrasound and converted to finite element based models. Model complexity of externally unsupported (aorta-only) models was complemented with inclusion of both soft tissue around the aorta and a spine support dorsal to the aorta. Computed 3-D motion of the aortic wall was verified by means of ultrasound speckle tracking. Resulting stress, strain, and estimated shear moduli were analyzed to quantify the effect of adding surrounding material supports.
An improved agreement was shown between the ultrasound measurements and the finite element tissue and spine models compared to the aorta-only models. Peak and 99-percentile Von Mises stress showed an overall decrease of 23-30%, while estimated shear modulus decreased with 12-20% after addition of the soft tissue. Shear strains in the aortic wall were higher in areas close to the spine compared to the anterior region.
Improving model complexity with surrounding tissue and spine showed a homogenization of wall stresses, reduction in homogeneity of shear strain at the posterior side of the AAA, and a decrease in estimated aortic wall shear modulus. Future research will focus on the importance of a patient-specific spine geometry and location.
本研究旨在探讨利用超声成像技术，研究周围组织（包括脊柱存在）对腹主动脉瘤壁应力分析和力学特性的影响。
使用 3D 超声采集 7 名 AAA 患者和 11 名健康志愿者的几何形状，并将其转换为基于有限元的模型。通过超声斑点跟踪技术验证了主动脉壁的计算三维运动。外部无支撑（仅主动脉）模型的模型复杂性通过纳入主动脉周围的软组织和主动脉背侧的脊柱支撑来补充。分析得到的应力、应变和估计的剪切模量，以量化添加周围材料支撑的效果。
与仅主动脉模型相比，超声测量值与有限元组织和脊柱模型之间的一致性得到了提高。添加软组织后，峰值和 99%Von Mises 应力总体降低了 23-30%，而估计的剪切模量降低了 12-20%。靠近脊柱区域的主动脉壁的剪切应变高于前侧区域。
通过增加周围组织和脊柱的模型复杂性，可使壁应力更加均匀，减少 AAA 后侧的剪切应变的不均匀性，并降低估计的主动脉壁剪切模量。未来的研究将集中在患者特异性脊柱几何形状和位置的重要性上。
