There is acknowledged variability in the Circle of Willis in the general population, yet the structure and function relationship of the cerebrovasculature is poorly understood. We aimed to demonstrate the feasibility of combining high resolution imaging techniques and computational fluid dynamics (CFD) to describe cerebrovascular structure and function in vivo. We examined the null hypothesis that monozygotic (MZ) twins (18-30yrs) would exhibit similar CoW structure and function. Six twin pairs underwent 3T magnetic resonance angiography of the head and neck and B-mode Doppler ultrasound for velocity and diameter recordings in the vertebral and internal carotid arteries under three conditions (rest, hypercapnia and exercise). Artery diameter, length, tortuosity and bifurcation angle were assessed in regions of interest of the CoW. CFD simulated hemodynamics to determine the cardiac-cycle time averaged wall shear stress (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT). We observed low and insignificant intra-class correlations (ICC) between twins in all regions for diameter (ICC range 0.000-0.657, P>0.05), two of four regions for length (ICC range 0.355-0.368, P>0.05), all regions for tortuosity (ICC range 0.270-0.505, P>0.05), and all bifurcation angles (ICC range 0.000-0.547, P> 0.05). Similarly, no significant correlations were apparent for cerebral blood flow or CFD-derived measures of TAWSS, OSI and RRT, at rest or in response to hypercapnia or exercise. Therefore differences exist in CoW structure and associated shear stress in response to physiological stimulation. These data suggest that the structure, function and health of cerebrovascular arteries are not primarily genetically dependent.

中文翻译：

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使用多模态成像和计算流体动力学评估同卵双胞胎对生理刺激的脑血管反应。

在一般人群中，威利斯环存在公认的变异性，但对脑血管系统的结构和功能关系知之甚少。我们旨在证明结合高分辨率成像技术和计算流体动力学 (CFD) 来描述体内脑血管结构和功能的可行性。我们检查了单卵 (MZ) 双胞胎 (18-30 岁) 将表现出相似的 CoW 结构和功能的零假设。六对双胞胎在三种情况（休息、高碳酸血症和运动）下接受了头颈部 3T 磁共振血管造影和 B 型多普勒超声检查椎体和颈内动脉的速度和直径记录。在 CoW 的感兴趣区域评估动脉直径、长度、曲折度和分叉角。CFD 模拟血流动力学以确定心动周期时间平均壁剪切应力 (TAWSS)、振荡剪切指数 (OSI) 和相对停留时间 (RRT)。我们观察到双胞胎在所有区域的直径（ICC 范围 0.000-0.657，P>0.05）、长度的四个区域中的两个（ICC 范围 0.355-0.368，P>0.05）之间的低且不显着的类内相关性 (ICC)，所有曲折区域（ICC 范围 0.270-0.505，P>0.05）和所有分叉角（ICC 范围 0.000-0.547，P>0.05）。同样，在休息或对高碳酸血症或运动的反应中，脑血流量或 CFD 衍生的 TAWSS、OSI 和 RRT 测量没有明显的相关性。因此，CoW 结构和响应生理刺激的相关剪切应力存在差异。这些数据表明，结构，