University Hospital Freiburg, Department of Radiology, Medical Physics, Germany.
Circ Cardiovasc Imaging. 2010 Nov;3(6):647-55. doi: 10.1161/CIRCIMAGING.110.958504. Epub 2010 Sep 16.
the purpose of this study was to analyze the in vivo distribution of absolute wall shear stress (WSS(abs)) and oscillatory shear index (OSI) in the carotid bifurcation and to evaluate its dependence on bifurcation geometry, the presence of internal carotid artery (ICA) stenosis, and recanalization therapy.
time-resolved 3D blood flow was acquired with flow-sensitive 4D MRI in 64 normal carotid bifurcations and 17 carotid arteries with moderate ICA stenosis (48±6%) or after surgical recanalization. Among 64 normal arteries, atherogenic wall parameters were consistently concentrated in proximal bulb regions of the common (CCA) and internal (ICA) carotid arteries. The fraction of the carotid bulb exposed to atherosclerosis-prone wall parameters (low WSS(abs) below and high OSI above group-defined 20% and 10% thresholds) was correlated with the individual bifurcation geometry. Multiple regressions revealed significant (P<0.01) relationships (β, 0.44 to 0.48) between the areas with atherosclerosis-prone wall parameters and the d(ICA)/d(CCA) diameter ratio. The size of regions exposed to high OSI demonstrated highly significant (P≤0.01) relationships with all analyzed geometry parameters (d(ICA)/d(CCA) β, 0.48; tortuosity β, ≤-0.56; bifurcation angle β, ≥0.47). Moderate ICA stenosis altered the distribution of wall parameters (45%/61% reduction of individually low WSS(abs)/high OSI in the proximal ICA), which were relocated to segments distal to the arterial stenosis. WSS(abs)/OSI topology after recanalization was similar compared with the normal wall parameter distribution.
flow-sensitive 4D MRI identified alterations in the segmental in vivo WSS distribution associated with atherosclerotic disease, surgical therapy, and individual bifurcation geometry and could be a valuable technique to assess the individual risk of flow-mediated atherosclerosis and carotid plaque progression.
本研究旨在分析颈内动脉分叉处绝对壁切应力（WSS(abs)）和振荡剪切指数（OSI）的体内分布，并评估其与分叉几何形状、颈内动脉（ICA）狭窄的存在以及再通治疗的关系。
使用血流敏感 4D MRI 采集 64 个正常颈动脉分叉处和 17 个 ICA 中度狭窄（48±6%）或手术后再通的颈动脉的时相分辨 3D 血流。在 64 个正常动脉中，动脉粥样硬化相关的壁参数集中于颈总动脉（CCA）和颈内动脉（ICA）的近端球部。暴露于易患动脉粥样硬化壁参数（低 WSS(abs)低于和高 OSI 高于组定义的 20%和 10%阈值）的颈动脉球部比例与个体分叉几何形状相关。多元回归显示，易患动脉粥样硬化壁参数的区域与 d(ICA)/d(CCA)直径比之间存在显著（P<0.01）的关系（β，0.44 至 0.48）。暴露于高 OSI 的区域大小与所有分析的几何形状参数之间存在显著（P≤0.01）的关系（d(ICA)/d(CCA)β，0.48；迂曲度β，≤-0.56；分叉角度β，≥0.47）。中度 ICA 狭窄改变了壁参数的分布（ICA 近端个体低 WSS(abs)/高 OSI 减少 45%/61%），这些参数被重新定位到动脉狭窄的远端节段。再通后的 WSS(abs)/OSI 拓扑与正常壁参数分布相似。
血流敏感 4D MRI 可识别与动脉粥样硬化疾病、手术治疗以及个体分叉几何形状相关的节段性体内 WSS 分布的改变，可能是评估血流介导的动脉粥样硬化和颈动脉斑块进展个体风险的有价值技术。
