School of Human Sciences, The University of Western Australia, Perth, Australia.
Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia.
J Appl Physiol (1985). 2020 Nov 1;129(5):1024-1032. doi: 10.1152/japplphysiol.00348.2020. Epub 2020 Sep 3.
There is acknowledged variability in the Circle of Willis (CoW) 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 tested our methodology by examining the null hypothesis that monozygotic twins (18-30 yr) 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. We 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 intraclass correlations (ICC) between twins in all regions for diameter (ICC range 0.000-0.657, > 0.05), two of four regions for length (ICC range 0.355-0.368, > 0.05), all regions for tortuosity (ICC range 0.270-0.505, > 0.05), and all bifurcation angles (ICC range 0.000-0.547, > 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. 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. Using a combination of magnetic resonance imaging, high-resolution Doppler ultrasound, and computational fluid dynamic modeling, we show that monozygotic twins exhibit differences in cerebrovascular structure and function when exposed to physiological stimuli. These data suggest that the morphology, function, and health of cerebrovascular arteries are not primarily genetically determined.
人们普遍承认 Willis 环（CoW）存在可变性，但脑脉管系统的结构和功能关系仍知之甚少。我们旨在展示结合高分辨率成像技术和计算流体动力学（CFD）来描述活体脑血管结构和功能的可行性。我们通过检验同卵双胞胎（18-30 岁）在 CoW 结构和功能上表现出相似性的零假设来验证我们的方法。六对双胞胎接受了头部和颈部的 3T 磁共振血管造影和椎动脉及颈内动脉的 B 型超声多普勒检查，以在三种情况下（休息、高碳酸血症和运动）记录速度和直径。在 CoW 的感兴趣区域评估了动脉直径、长度、迂曲度和分叉角度。我们模拟了血液动力学以确定心动周期时均壁切应力（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，>0.05）、四个区域中的两个的长度（ICC 范围 0.355-0.368，>0.05）、所有区域的迂曲度（ICC 范围 0.270-0.505，>0.05）和所有分叉角度（ICC 范围 0.000-0.547，>0.05）的低且无统计学意义的组内相关系数（ICC）。同样，在休息或对高碳酸血症或运动的反应中，脑血流或 CFD 衍生的 TAWSS、OSI 和 RRT 测量值也没有明显的相关性。因此，在生理刺激下，CoW 结构和相关剪切应力存在差异。这些数据表明，脑血管的结构、功能和健康状况不是主要由遗传决定的。人们普遍承认 Willis 环在普通人群中存在可变性，但脑脉管系统的结构和功能关系仍知之甚少。我们使用磁共振成像、高分辨率多普勒超声和计算流体动力学建模相结合的方法，证明同卵双胞胎在暴露于生理刺激时表现出脑血管结构和功能的差异。这些数据表明，脑血管的形态、功能和健康状况不是主要由遗传决定的。
