Determinants of Intracranial Aneurysm Growth

摘要： 颅内动脉瘤存在巨大的死亡或毁灭性损伤风险，无论是由于占位效应， 出血首次就诊时检测到的动脉瘤尺寸范围很广。然而， 动脉瘤的发展速度长期以来，人们一直怀疑血液动力学 在动脉瘤的发生和破裂中起重要作用，但据我们所知，没有文献 证明动脉瘤的血流动力学描述符可以预测未来的生长。 国际未破裂颅内动脉瘤研究的最新结果表明， 尝试修复直径小于7 mm的动脉瘤超出了该介入的益处。 因此，现在有一组患有囊性颅内动脉瘤的患者没有得到治疗， 并且可以进行非侵入性成像。这些患者是更广泛的患者群体的一部分， 没有安全有效的干预措施的颅内循环动脉瘤。 该项目的目标是每两年用非侵入性磁共振技术监测这类患者 显像使用从患者特异性体内成像获得的边界值（几何和速度）， 将进行计算流体动力学（CFD）模拟，以确定血流动力学条件 在每个动脉瘤。动脉瘤管腔体积和/或腔内血栓体积随时间的进展 将从联合配准的系列成像研究中测量。不同候选人之间的关系 将寻求血液动力学变量和观察到的动脉瘤生长。具体来说，我们假设， 指定低壁剪切应力阈值，壁剪切应力低于阈值的表面积越大 该阈值越大，动脉瘤体积随时间的增加越大。 除了使用已经建立的标准方法外，我们还将开发新的成像能力， 并且将实现对整个血管区域的流速的更全面的测量 兴趣我们的计算流体力学方法将扩展到非牛顿效应模型， 将使用测量值来选择最合适的模型。随着这些新工具的出现， 将用于提高我们方法的准确性。该项目代表了转化研究的一项努力 针对神经血管疾病的重要组成部分。

Abstract: Intracranial aneurysms present a formidable risk of death or devastating injury either from mass effect or hemorrhage. Aneurysms are detected with a broad range of sizes on first presentation. However, little is known about the rate of progression of aneurysms over time. It has long been suspected that hemodynamic forces play an important role in the genesis and rupture of aneurysms, but there is, to our knowledge, no literature that demonstrates which hemodynamic descriptors of an aneurysm are predictive of future growth. Recent results from the International Study of Unruptured Intracranial Aneurysms demonstrate that the risk of attempting a repair of aneurysms smaller than 7 mm in diameter exceeds the benefit from that intervention. There is now, therefore, a group of patients with saccular intracranial aneurysms who are not being treated, and who can be followed by non-invasive imaging. These patients are part of a broader group of patients with aneurysms of the intracranial circulation for whom there are no safe and effective interventions. The goal of this project is to monitor such patients on a bi-annual basis with non-invasive Magnetic Resonance Imaging. Using boundary values (geometric and velocity) obtained from patient-specific in-vivo imaging, Computational Fluid Dynamics (CFD) simulations will be performed to determine the hemodynamic conditions in each aneurysm. Progression over time in aneurysm lumen volume and/or volume of intralumenal thrombus will be measured from co-registered serial imaging studies. A relationship between different candidate hemodynamic variables and observed aneurysm growth will be sought. Specifically, we hypothesize that, specifying a low wall shear stress threshold value, the larger the surface area is with wall shear stress below that threshold value the greater will be the increase in aneurysm volume over time. In addition to using the standard methodology already established, we will develop new imaging capabilities, and will implement more comprehensive measurements of flow velocities throughout the vascular territory of interest. Our CFD methods will be extended to model non-Newtonian effects, and the in-vivo velocity measurements will be used to select which model is most suitable. As these new tools become available they will be used to improve the accuracy of our methods. This project represents an effort in translational research directed at an important component of neurovascular disorders.