Abstract：
The Circle of Willis (CoW) is a ring-like network of blood vessels that perfuses the brain. Flow in the collateral pathways that connect major arterial inputs in the CoW change dynamically in response to vessel narrowing or occlusion. Vasospasm is an involuntary constriction of blood vessels following subarachnoid hemorrhage (SAH), which can lead to stroke. This study investigated interactions between localization of vasospasm in the CoW, vasospasm severity, anatomical variations, and changes in collateral flow directions. Patient-specific computational fluid dynamics (CFD) simulations were created for 25 vasospasm patients. Computed tomographic angiography scans were segmented capturing the anatomical variation and stenosis due to vasospasm. Transcranial Doppler ultrasound measurements of velocity were used to define boundary conditions. Digital subtraction angiography was analyzed to determine the directions and magnitudes of collateral flows as well as vasospasm severity in each vessel. Percent changes in resistance and viscous dissipation were analyzed to quantify vasospasm severity and localization of vasospasm in a specific region of the CoW. Angiographic severity correlated well with percent changes in resistance and viscous dissipation across all cerebral vessels. Changes in flow direction were observed in collateral pathways of some patients with localized vasospasm, while no significant changes in flow direction were observed in others. CFD simulations can be leveraged to quantify the localization and severity of vasospasm in SAH patients. These factors as well as anatomical variation may lead to changes in collateral flow directions. Future work could relate localization and vasospasm severity to clinical outcomes like the development of infarct.
摘要：
威利斯环（CoW）是一个环状的血管网络，灌注大脑。连接CoW中的主要动脉输入的侧支通路中的流量响应于血管变窄或闭塞而动态变化。血管痉挛是蛛网膜下腔出血（SAH）后血管的不自主收缩，会导致中风.这项研究调查了CoW中血管痉挛定位之间的相互作用，血管痉挛的严重程度，解剖变异，以及抵押品流动方向的变化。针对25名血管痉挛患者创建了患者特定的计算流体动力学（CFD）模拟。对计算机断层扫描血管造影扫描进行分段，以捕获由于血管痉挛引起的解剖变化和狭窄。经颅多普勒超声测量速度用于定义边界条件。对数字减影血管造影进行了分析，以确定每条血管的侧支血流的方向和大小以及血管痉挛的严重程度。分析了阻力和粘性耗散的百分比变化，以量化CoW特定区域的血管痉挛严重程度和血管痉挛的定位。血管造影严重程度与所有脑血管的阻力和粘性耗散百分比变化密切相关。在一些局部血管痉挛患者的侧支通路中观察到血流方向的变化，而在其他方面没有观察到流动方向的显著变化。CFD模拟可用于量化SAH患者血管痉挛的定位和严重程度。这些因素以及解剖变化可能导致侧支流动方向的变化。未来的工作可能将定位和血管痉挛的严重程度与临床结果相关，例如梗塞的发展。
