Determinants of Intracranial Aneurysm Growth

描述(由申请人提供)：颅内动脉瘤呈现出巨大的死亡或破坏性损伤的风险，无论是由于肿块效应还是出血。首次发现的动脉瘤大小不一。然而，人们对动脉瘤随时间的进展速度知之甚少。长期以来，人们一直怀疑血流动力在动脉瘤的发生和破裂中起着重要作用，但据我们所知，还没有文献证明动脉瘤的哪些血流动力学描述可以预测未来的生长。国际未破裂颅内动脉瘤研究最近的结果表明，试图修补直径小于7毫米的动脉瘤的风险超过了这种干预的好处。因此，现在有一群没有接受治疗的囊性颅内动脉瘤患者，他们可以通过非侵入性成像进行追踪。这些患者是更广泛的颅内循环动脉瘤患者中的一部分，对这些患者来说，没有安全有效的干预措施。该项目的目标是用非侵入性磁共振成像每两年监测一次这类患者。使用从患者特定的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)模拟以确定每个动脉瘤的血流动力学状况。共同注册的系列成像研究将测量动脉瘤腔体积和/或腔内血栓体积随时间的进展。不同的候选血流动力学变量和观察到的动脉瘤生长之间的关系将被寻求。具体地说，我们假设，指定一个较低的壁切应力阈值，壁切应力低于该阈值的表面积越大，随着时间的推移，动脉瘤体积增加的幅度就越大。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，并将在感兴趣的血管区域实施更全面的血流速度测量。我们的CFD方法将扩展到模拟非牛顿效应，并将使用体内速度测量来选择最适合的模型。随着这些新工具的出现，它们将被用来提高我们方法的准确性。这个项目代表了针对神经血管疾病的一个重要组成部分的翻译研究的努力。公共卫生相关性：这项研究将确定颅内动脉瘤的生长与血流动力之间的关系。这些信息将被用来指导临床医生考虑哪些介入治疗，以及何时可能最好地实施这些治疗。该项目将提供对动脉瘤进展的潜在机制的洞察，并可能有助于指导这种毁灭性疾病的治疗。

DESCRIPTION (provided by applicant): 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 intraluminal 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 a important component of neurovascular disorders. PUBLIC HEALTH RELEVANCE: This study will determine the relationship between growth of intracranial aneurysms and hemodynamic forces. That information will be used to guide clinicians as to what interventional treatments might be considered, and when they might best be implemented. The project will provide insight into the underlying mechanisms of aneurysm progression and could help in guiding treatment for this devastating condition.