Department of Applied Mechanics and Biomedical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, 695011, India.
Med Eng Phys. 2024 Aug;130:104211. doi: 10.1016/j.medengphy.2024.104211. Epub 2024 Jul 20.
Imaging methodologies such as, computed tomography (CT) aid in three-dimensional (3D) reconstruction of patient-specific aneurysms. The radiological data is useful in understanding their location, shape, size, and disease progression. However, there are serious impediments in discerning the blood vessel wall thickness due to limitations in the current imaging modalities. This further restricts the ability to perform high-fidelity fluid structure interaction (FSI) studies for an accurate assessment of rupture risk. FSI studies would require the arterial wall mesh to be generated to determine realistic maximum allowable wall stresses by performing coupled calculations for the hemodynamic forces with the arterial walls.
In the present study, a novel methodology is developed to geometrically model variable vessel wall thickness for the lumen isosurface extracted from CT scan slices of patient-specific aneurysms based on clinical and histopathological inputs. FSI simulations are carried out with the reconstructed models to assess the importance of near realistic wall thickness model on rupture risk predictions.
During surgery, clinicians often observe translucent vessel walls, indicating the presence of thin regions. The need to generate variable vessel wall thickness model, that embodies the wall thickness gradation, is closer to such clinical observations. Hence, corresponding FSI simulations performed can improve clinical outcomes. Considerable differences in the magnitude of instantaneous wall shear stresses and von Mises stresses in the walls of the aneurysm was observed between a uniform wall thickness and a variable wall thickness model.
In the present study, a variable vessel wall thickness generation algorithm is implemented. It was shown that, a realistic wall thickness modeling is necessary for an accurate prediction of the shear stresses on the wall as well as von Mises stresses in the wall. FSI simulations are performed to demonstrate the utility of variable wall thickness modeling.
影像学方法（如计算机断层扫描（CT））有助于对患者特定的动脉瘤进行三维（3D）重建。放射学数据有助于了解其位置、形状、大小和疾病进展。然而，由于当前成像方式的限制，在辨别血管壁厚度方面存在严重障碍。这进一步限制了进行高精度流体结构相互作用（FSI）研究的能力，无法准确评估破裂风险。FSI 研究需要生成动脉壁网格，通过对血流动力学力与动脉壁进行耦合计算，确定现实的最大允许壁应力，从而进行准确的评估。
本研究提出了一种新的方法，基于临床和组织病理学输入，从患者特定动脉瘤的 CT 扫描切片中提取管腔等表面，对可变血管壁厚度进行几何建模。使用重建模型进行 FSI 模拟，以评估接近真实壁厚度模型对破裂风险预测的重要性。
在手术过程中，临床医生经常观察到半透明的血管壁，表明存在薄的区域。需要生成可变血管壁厚度模型，体现壁厚度的渐变，更接近这些临床观察。因此，相应的 FSI 模拟可以改善临床结果。在均匀壁厚度模型和可变壁厚度模型之间，观察到动脉瘤壁的瞬时壁剪切应力和 von Mises 应力的幅度有很大差异。
本研究实现了一种可变血管壁厚度生成算法。结果表明，进行准确的壁剪切应力预测和壁内 von Mises 应力预测，需要进行现实的壁厚度建模。进行 FSI 模拟以证明可变壁厚度建模的实用性。
